David Byrne – Once in a lifetime

Databases come in all different shapes and sizes. They can be flat files of ASCII data (like Access or Q&A) or complex binary tree structures (Oracle or Sybase).
In any form, a database is a data store, or a place that holds data.
That is the job of the database management system, or DBMS. Some DBMSs are relational. Those are RDBMS. The relational part refers to the fact that separate collections of data within the reaches of the RDBMS can be looked at together in unison. The RDBMS is responsible for ensuring the integrity of the database.
Sometimes, things will get out of whack and the RDBMS will keep all that data in line.

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A database is a collection of related data.
A database management system (DBMS) is a collection of programs that enables users to create and maintain a database.
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To control redundancy.
To restrict unauthorized access.
To provide persistent storage for program objects and data structures.
To permit inference and actions using rules.
To provide multiple user interfaces.
To representing complex relationships among data.
To enforce integrity constraints.
To provide backup and recovery.

The evolution of relational data storage began in 1970 with the work of Dr.
E. F. Codd, who proposed a set of 12 rules for identifying relationships between pieces of data. Codd's rules formed the basis for the development of systems to manage data. Today, Relational Database Management
Systems (RDBMS) are the result of Codd's vision.
Data in an RDBMS are stored as rows of distinct information in tables. A structured language is used to query (retrieve), store and change the data.
The Structured Query Language (SQL) is an ANSI standard, and all major commercial RDBMS vendors provide mechanisms for issuing SQL commands.

The early development of RDBMS applications utilized an integrated model of user interface code,
Application code and database libraries. This single binary model ran only on a local machine, typically a mainframe. The applications were simple but inefficient and did not work over LANs. The model did not scale the application and user interface code was tightly coupled to the database libraries.
The monolithic single-tier database design

Two-Tier Database Design
Two-tier model appeared with the advent of server technology. Communication-protocol development and extensive use of local and wide area networks allowed the database developer to create an application front end that accessed data through a connection ( socket ) to the back-end server. A two-tier database design, where the client software is connected to the database through a socket connection.
The two-tier database design
Client programs (applying a user interface) send SQL requests to the database server. The server returns the appropriate results, and the client is responsible for the formatting and display of the data. Clients still use a vendor-provided library of functions that manage the communication between client and server. Most of these libraries are written in either the C language or Perl.
Commercial database vendors realized the potential for adding intelligence to the database server. They created proprietary techniques that allowed the database designer to develop macro programs for simple data manipulation. These macros, called stored procedures, can cause problems relating to version control and maintenance. Because a stored procedure is an executable program living on the database, it is possible for the stored procedure to attempt to access named columns of a database table after the table has been changed.
For example , if a column with the name id is changed to cust_id, the meaning of the original stored procedure is lost. The advent of triggers, which are stored procedures executed automatically when some action (such as insert) happens with a particular table or tables, can compound these difficulties when the data returned from a query are not expected. Again, this can be the result of the trigger reading a table column that has been altered.

 The vendor-provided library limits them. Switching from one database vendor to another requires a rewrite of a significant amount of code to the client application.
 Version control is an issue. When the vendor updates the client-side libraries, the applications that utilize the database must be recompiled and redistributed.
 Vendor libraries deal with low-level data manipulation. Typically, the base library only deals with queries and updates of single rows or columns of data. This can be enhanced on the server side by creating a stored procedure, but the complexity of the system then increases.
 All of the intelligence associated with using and manipulating the data is implemented in the client application, creating large client-side runtimes. This drives up the cost of each client set.

In a multi-tier design, the client communicates with an intermediate server that provides a
Layer of abstraction from the RDBMS. The intermediate layer is designed to handle multiple
Client requests and manage the connection to one or more database servers. There does not have to be just three tiers, but conceptually this is the next step.
Three-Tier Database Design

 It is multithreaded to manage multiple client connections simultaneously.
 It can accept connections from clients over a variety of vendor-neutral protocols (from HTTP to TCP/IP), then hand off the requests to the appropriate vendor-specific database servers, returning the replies to the appropriate clients.
 It can be programmed with a set of "business rules" that manage the manipulation of the data. Business rules could include anything from restricting access to certain portions of data to making sure that data is properly formatted before being inserted or updated.
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
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It prevents the client from becoming too heavy by centralizing processintensive tasks and abstracting data representation to a higher level.
It isolates the client application from the database system and frees a company to switch database systems without having to rework the business rules.
It can asynchronously provide the client with the status of a current data table or row.

Sybase/ SQL Server 6.0
6.5
7.0
2000
2005
7.x
8.0.x
8.1.x ( aka 8i)
9.2
10G
NCR Teradata
Ingres
Informix
Sybase
MySQL
Gupta/Centura -SQLbase
DBase
Paradox . . . Many others

.

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Tables
 Columns
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Indexes
Data-types
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Primary key
Foreign key
Views
Table-spaces
Partitions
Constraints
Synonyms
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Packages
Triggers
Procedures
Functions
Constraints
Sequences

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A relational database system contains one or more objects called tables. The data or information for the database are stored in these tables. Tables are uniquely identified by their names and are comprised of columns and rows. Columns contain the column name, data type, and any other attributes for the column. Rows contain the records or data for the columns. Here is a sample table called "weather".
Tucson city
Phoenix
Flagstaff
Weather state
Arizona
Arizona
Arizona
 city, state, high, and low are the columns. The rows contain the data for this table:
San Diego California
Albuquerque New Mexico 80 high
105
101
88
77
90
92
69
60
72 low

A primary key is a table column that can be used to uniquely identify every row of the table. Any column that has this property will do -these columns are called candidate keys. A table can have many candidate keys but only one primary key. The primary key cannot be null.
FooNumber FirstName LastName BarTab
21
32
Fred
Bill
Jones
Smith
47
23
87 Wendy Jones -
32 Bob Stikino 943

 A is a primary key consisting of more than one column. In the above example, the combinations (RecordNo,FirstName), (RecordNo,Lastname),
(RecordNo,FirstName,Lastname), and (FirstName,LastName) are all candidate keys. Any combination including Age is not a candidate key because it contains a null.
 Often, database designers add an extra column to their table designs, a column defined as an integer, which will hold a number. In Microsoft
Access, this is an autonumber , in MySQL it's an auto-increment , in Oracle it's a sequence , and in SQL/Server it's an identity column. As these names suggest, this integer is automatically assigned by the database, usually incrementally, sometimes using an initial value and increment that you can specify. Some databases allow these numbers to be generated randomly.
 The purpose of this type of automatically generated number is to act as the surrogate primary key, usually in those situations similar to the above where candidate keys are multi-column. The awkwardness of a multicolumn candidate key becomes apparent as soon as you define a foreign key on it.

ClrPK A foreign key is a column, or combination of columns, that contain values that are found in the primary key of some table (including, possibly, itself).
A foreign key may be null, and almost always is not unique.That last statement may be counterintuitive, so let's take another example. Here we have two tables that are related via a foreign key –
10
20
30
40
As you can see, the ClrFK column in the second table is a foreign key to the ClrPK primary key in the first table. Notice that the ClrPK values are unique and not null, but the ClrFK values may be null and often repeat. A null foreign key means that that particular row does not participate in the relationship. The fact that many foreign key values repeat simply reflects the fact that it's a one-tomany relationship.
In a one-to-many relationship, the primary key has the "one" value, and the foreign key has the "many" values. The trick to remembering this is to keep in mind that the primary key must be unique.
AdjPK
904
913
937
941
954
979
991
ColourName yellow red green blue
AdjectiveName angry envious lazy lonely fearful jealous furious
40
10
30
20
ClrFK
20
-
30

Null means either "don't know" or "not applicable" -- it's not really the same as zero or any other default value, but more importantly, null is treated quite differently from other values in SQL, because it literally has no value.
Here's an example of a "don't know" null ->
As you can see, Fred's value is null, which you could interpret as meaning that Fred didn't take the test (maybe he has a medical exemption and will take the test another day). It would be wrong to assign a zero, because that would be interpreted as Fred having taken the test and not getting a single answer right!
Student
Joe
Bill
Mary
Fred
Sam
73
56
TestResult
87 null
92

Now consider the following query –
SELECT AVG(TestResult) FROM Students;
Aggregate functions like AVG() and SUM() ignore nulls, so this query will return (87+73+56+92)/4=77, which is certainly better than 87+73+56+0+92)/5=61.6 which you'd get using a zero default. Often a default value is just wrong for a column where you expect to take aggregates.
An example of a column that would take a "not applicable" null is Date Terminated in a human resources database, where the value would be null for all active employees. To test for nulls, you can filter them out in the WHERE clause –
SELECT EmployeeID , (DateTerminated - DateHired) AS LengthOfService FROM EmployeeTable
WHERE DateTerminated IS NOT NULL which would give results only for terminated employees. If you didn't have the WHERE clause, the above query would return null for every active employee, because any expression involving a null yields a null result.
Alternatively, you can use the COALESCE function to supply a non-null value –
SELECT EmployeeID , ( COALESCE(DateTerminated,GETDATE()) - DateHired) AS LengthOfService
FROM EmployeeTable where GETDATE() returns today's date and therefore provides an accurate measure for the length of service of active employees. So for terminated employees, DateTerminated is not null, and the calculation is the same as above, while for active employees, DateTerminated is null so COALESCE uses today's date instead.

 SQL or SEQUEL ?
 SQL (pronounced "ess-que-el")
 The acronym SQL stands for S tructured Q uery L anguage
 SQL is used to communicate with a database. According to ANSI (American National
Standards Institute), it is the standard language for relational database management systems. SQL statements are used to perform tasks such as update data on a database, or retrieve data from a database. Some common relational database management systems that use SQL are: Oracle, Sybase, Microsoft SQL Server, Access, Ingres, etc.
Although most database systems use SQL, most of them also have their own additional proprietary extensions that are usually only used on their system. However, the standard
SQL commands such as "Select", "Insert", "Update", "Delete", "Create", and "Drop" can be used to accomplish almost everything that one needs to do with a database.
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
Some people claim that this is a bad name, because
 SQL isn't (properly) structured

 it's more than just queries (e.g. insert, update, delete) it isn't a real computing language (Very Debatable)
In any case, SQL is a database query language that was adopted as an industry standard in 1986. It has undergone two important revisions, SQL2 (also called SQL-92), and SQL3
(also called SQL-99).

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The select statement is used to query the database and retrieve selected data that match the criteria that you specify. Here is the format of a simple select statement: select "column1" [,"column2",etc] from
"tablename" [where "condition"];
[ ] = optional
The column names that follow the select keyword determine which columns will be returned in the results. You can select as many column names that you'd like, or you can use a "*" to select all columns.
The table name that follows the keyword
from specifies the table that will be queried to retrieve the desired results.
The where clause (optional) specifies which data values or rows will be returned or displayed, based on the criteria described after the keyword where.
Conditional selections used in the where clause:
=
>
<
>=
<=
<>
LIKE
Equal
Greater than
Less than
Greater than or equal
Less than or equal
Not equal to
*See next page – Special Operator

 select first, last, city from empinfo; select last, city, age from empinfo where age > 30;
 select first, last, city, state from empinfo where first LIKE 'J%';
 select * from empinfo;
 select first, last, from empinfo where last LIKE
'%s';
 select first, last, age from empinfo where last
LIKE '%illia%';
 select * from empinfo where first = 'Eric'; first
John
Mary
Eric
Mary
An n
Ginger
Sebastia n
Gus
Mary
An n
Erica
Leroy
Elroy last
Sample Table: empinfo id ag e city
Jones
Jones
Edward s
9998
0 45
9998
2 25
8823
2 32
Payson
Payson
San Diego
Edward s
Phoenix
Howell
Smith
Gray
May
William s
Brown
Cleaver
8823
3 32
9800
2 42
9200
1 23
2232
2 35
3232
6 52
3232
7 60
3238
0 22
3238
2 22
Cottonwoo d
Gila Bend
Bagdad
Tucson
Show Low
Pinetop
Globe state
Arizona
Arizona
Californi a
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona

 select first, last, city from empinfo; select last, city, age from empinfo where age >
30; last
Jones
Edwards
Edwards
Howell
Gray
May
Williams city
Payson
San Diego
Phoenix
Cottonwood
Bagdad
Tucson
Show Low
42
35
52
60 age
45
32
32 first
John
Mary
Eric
Mary Ann
Ginger
Sebastia
Gus n
Mary Ann
Erica
Leroy
Elroy last
Sample Table: empinfo id ag e city
Jones
Jones
9998
0
9998
2
45
25
Payson
Payson
Edward s
Edward s
Howell
Smith
Gray
May
Williams
Brown
Cleaver
8823
8823
2
3
9800
2
9200
1
2232
2
3232
6
3232
7
3238
0
3238
2
32
32
42
23
35
52
60
22
22
San Diego
Phoenix
Cottonwoo d
Gila Bend
Bagdad
Tucson
Show Low
Pinetop
Globe state
Arizona
Arizona
Californi a
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona

 select first, last, city, state from empinfo where first LIKE 'J%'; first
John last
Jones city state
Payson Arizona first
John
Mary
Eric
Mary Ann
Ginger last
Jones
Sample Table: empinfo id age
99980 45
Jones 99982 25
Edwards 88232 32
Edwards
Howell
Sebastian Smith
Gus Gray
88233
98002
92001
22322
32
42
23
35 city
Payson
Payson
San Diego
Phoenix
Cottonwood
Gila Bend
Bagdad
Mary Ann
Erica
Leroy
Elroy
May
Williams 32327 60
Brown
Cleaver
32326 52
32380
32382
22
22
Tucson
Show Low
Pinetop
Globe state
Arizona
Arizona
California
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona

 select * from empinfo; first
John
Mary
Eric
Mary Ann
Ginger
Sebastian
Gus
Mary Ann
Erica
Leroy
Elroy last
Jones
Jones
Edwards
Edwards
Howell
Smith
Gray
May
Williams
Brown
Cleaver id
99980
99982
88232
88233
98002
92001
22322
32326
32327
32380
32382
32
32
42
23
35 age
45
25
52
60
22
22 city
Payson
Payson
San Diego
Phoenix
Cottonwood
Gila Bend
Bagdad
Tucson
Show Low
Pinetop
Globe state
Arizona
Arizona
California
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Eric first
John
Mary
Mary Ann
Ginger
Sebastian
Gus last
Sample Table: empinfo id ag e city
Jones 99980 45 Payson
Jones 99982 25 Payson
Edwards 88232 32 San Diego
Edwards 88233 32 Phoenix
Howell
Smith
Gray
98002 42 Cottonwood
92001
22322
23
35
Gila Bend
Bagdad state
Arizona
Arizona
California
Arizona
Arizona
Arizona
Arizona
Mary Ann May 32326 52 Tucson Arizona
Erica
Leroy
Elroy
Williams 32327 60 Show Low
Brown
Cleaver
32380
32382
22 Pinetop
22 Globe
Arizona
Arizona
Arizona

select first, last, from empinfo where last
LIKE '%s'; first
John
Mary
Eric last
Sample Table: empinfo id age city
Jones
Jones
99980
99982
45
25
Payson
Payson
Edwards 88232 32 San Diego
Mary Ann Edwards 88233 32 Phoenix first
John
Mary
Eric
Mary Ann
Erica last
Jones
Jones
Edwards
Edwards
Williams
Ginger Howell
Sebastian Smith
Gus Gray
Mary Ann May
Erica
Leroy
Elroy
98002 42
92001 23
22322 35
32326 52
Williams 32327 60
Brown
Cleaver
32380
32382
22
22
Cottonwood Arizona
Gila Bend
Bagdad
Arizona
Arizona
Tucson
Show Low
Pinetop
Globe state
Arizona
Arizona
California
Arizona
Arizona
Arizona
Arizona
Arizona

select first, last, age from empinfo where last
LIKE '%illia%'; first
John
Mary
Eric last
Sample Table: empinfo id age city
99980 45 Payson Jones
Jones 99982 25 Payson
Edwards 88232 32 San Diego state
Arizona
Arizona
California first
Erica last
Williams age
60
Mary Ann Edwards 88233 32 Phoenix Arizona
Ginger Howell
Sebastian Smith
Gus Gray
98002 42 Cottonwood Arizona
92001 23 Gila Bend
22322 35 Bagdad
Arizona
Arizona
Mary Ann May
Erica
Leroy
Elroy
32326 52 Tucson Arizona
Williams 32327 60 Show Low
Brown 32380 22 Pinetop
Cleaver 32382 22 Globe
Arizona
Arizona
Arizona

select * from empinfo where first = 'Eric'; first last id age city state
Eric Edwards 88232 32 San Diego California first
John
Mary
Eric last
Jones
Jones
Edwards
Mary Ann Edwards
Sample Table: empinfo id
99980
99982
88232 age
45
25
32
88233 32 city
Payson
Payson
San Diego
Phoenix
Erica
Leroy
Elroy
Ginger Howell
Sebastian Smith
Gus Gray
Mary Ann May
98002
92001
22322
42
23
35
Cottonwood
Gila Bend
Bagdad
32326 52 Tucson
Williams
Brown
Cleaver
32327 60
32380 22
32382 22
Show Low
Pinetop
Globe
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona
Arizona state
Arizona
Arizona
California
Arizona

first
John
Mary
Eric last
Sample Table: empinfo id age city
Jones 99980 45 Payson
Jones 99982 25 Payson
Edwards 88232 32 San Diego state
Arizona
Arizona
California
Mary Ann Edwards 88233 32 Phoenix Arizona
Ginger Howell
Sebastian Smith
Gus Gray
98002 42 Cottonwood Arizona
92001 23 Gila Bend Arizona
22322 35 Bagdad Arizona
Mary Ann May
Erica
Leroy
Elroy
32326 52 Tucson Arizona
Williams 32327 60 Show Low
Brown 32380 22 Pinetop
Cleaver 32382 22 Globe
Arizona
Arizona
Arizona
The LIKE pattern matching operator can also be used in the conditional selection of the where clause. Like is a very powerful operator that allows you to select only rows that are "like" what you specify. The percent sign "%“ can be used as wild card to match any possible character that might appear before or after the characters specified.
For example: select first, last, city from empinfo where
First LIKE 'Er%';
This SQL statement will match any first names that start with 'Er'.
Strings must be in single quotes.
Or you can specify, select first, last from empinfo where last
LIKE '%s';
This statement will match any last names that end in a 's'.
select * from empinfo where first = 'Eric';
This will only select rows where the first name equals 'Eric' exactly.

JOIN is a query clause that can be used with the SELECT, UPDATE, and DELETE data query statements to simultaneously affect rows from multiple tables. There are several distinct types of JOIN statements that return different data result sets.
Joined tables must each include at least one field in both tables that contain comparable data. For example, if you want to join a Customer table and a
Transaction table, they both must contain a common element, such as
CustomerID column, to serve as a key on which the data can be matched. Tables can be joined on multiple columns so long as the columns have the potential to supply matching information. Column names across tables don't have to be the same, although for readability this standard is generally preferred.
When you do use like column names in multiple tables, you must use fully qualified column names. This is a “dot” notation that combines the names of tables and columns. For example, if I have two tables, Customer and Transaction, and they both contain the column CustomerID
, I’d use the dot notation, as in
Customer.CustomerID and Transaction.CustomerID, to let the database know which column from which table I’m referring.
Now that we’ve examined the basic theory, let’s take a look at the various types of joins and examples of each.

A basic JOIN statement has the following format:
SELECT Customer.CustomerID, TransID, TransAmt FROM Customer JOIN Transaction
ON Customer.CustomerID = Transaction.CustomerID;
In practice, you'd never use the example above because the type of join is not specified. In this case,
SQL Server assumes an INNER JOIN. You can get the equivalent to this query by using the statement:
SELECT Customer.CustomerID, TransID, TransAmt FROM Customer, Transaction;
However, the example is useful to point out a few noteworthy concepts:
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TransID and TransAmt do not require fully qualified names because they exist in only one of the tables. You can use fully qualified names for readability if you wish.
The Customer table is considered to be the “left” table because it was called first. Likewise, the
Transaction table is the “right” table.
You can use more than two tables, in which case each one is “naturally” joined to the cumulative result in the order they are listed, unless controlled by other functionality such as “join hints” or parenthesis.
You may use WHERE and ORDER BY clauses with any JOIN statement to limit the scope of your results. Note that these clauses are applied to the results of your JOIN statement.
SQL Server does not recognize the semicolon (;), but I use it in the included examples to denote the end of each statement, as would be expected by most other RDBMSs.
Another addition to your SQL toolbox Although the JOIN statement is often perceived as a complicated concept, you will see that it’s a powerful timesaving resource that’s relatively easy to understand. Use this functionality to get related information from multiple tables with a single query and to skillfully reference normalized data. Once you’ve mastered JOINs, you can elegantly maneuver within even the most complex database .

select * from A, B where A.x = B.y

(database)outer join - A less commonly used variant of the inner join relational database operation. An inner join selects rows from two tables such that the value in one column of the first table also appears in a certain column of the second table. For an outer join, the result also includes all rows from the first operand ("left outer join", "*="), or the second operand ("right outer join",
"=*"), or both ("full outer join", "*=*"). A field in a result row will be null if the corresponding input table did not contain a matching row.
For example, if we want to list all employees and their employee number, but not all employees have a number, then we could say (in SQL ):
SELECT employee.name, empnum.number WHERE employee.id *= empnum.id
The "*=" means "left outer join" and means that all rows from the
"employee" table will appear in the result, even if there is no match for their ID in the empnum table.

The CROSS JOIN has earned a bad reputation because it’s very resource intensive and returns results of questionable usefulness. When you use the CROSS JOIN, you're given a result set containing every possible combination of the rows returned from each table. Take the following example:
SELECT CustomerName, TransDate, TransAmt FROM Customer CROSS JOIN
Transaction;
With the CROSS JOIN, you aren’t actually free to limit the results, but you can use the ORDER BY clause to control the way they are returned. If the tables joined in this example contained only five rows each, you would get 25 rows of results. Every CustomerName would be listed as associated with every TransDate and TransAmt.
I really did try to come up with examples where this function was useful, and they were all very contrived. However, I’m sure someone out there is generating lists of all their products in all possible colors or something similar, or we wouldn’t have this wonderful but dangerous feature.

When you perform an INNER JOIN, only rows that match up are returned. Any time a row from either table doesn’t have corresponding values from the other table, it is disregarded. Because stray rows aren’t included, you don’t have any of the “left” and “right” nonsense to deal with and the order in which you present tables matters only if you have more than two to compare. Since this is a simple concept, here’s a simple example:
SELECT CustomerName, TransDate FROM Customer INNER JOIN
Transaction ON Customer.CustomerID = Transaction.CustomerID;
If a row in the Transaction table contains a CustomerID that’s not listed in the
Customer table, that row will not be returned as part of the result set. Likewise, if the Customer table has a CustomerID with no corresponding rows in the Transaction table, the row from the Customer table won’t be returned.

OUTER JOINs, sometimes called “complex joins,” aren’t actually complicated. They are so-called because SQL Server performs two functions for each OUTER JOIN.
The first function performed is an INNER JOIN. The second function includes the rows that the INNER
JOIN would have dropped. Which rows are included depends on the type of OUTER JOIN that is used and the order the tables were presented.
There are three types of an OUTER JOIN: LEFT, RIGHT, and FULL. As you’ve probably guessed, the
LEFT OUTER JOIN keeps the stray rows from the “left” table (the one listed first in your query statement). In the result set, columns from the other table that have no corresponding data are filled with NULL values. Similarly, the RIGHT OUTER JOIN keeps stray rows from the right table, filling columns from the left table with NULL values. The FULL OUTER JOIN keeps all stray rows as part of the result set. Here is your example:
SELECT CustomerName, TransDate, TransAmt FROM Customer LEFT OUTER JOIN Transaction ON
Customer.CustomerID = Transaction.CustomerID;
Customer names that have no associated transactions will still be displayed. However, transactions with no corresponding customers will not, because we used a LEFT OUTER JOIN and the Customer table was listed first.
In SQL Server, the word OUTER is actually optional.
The clauses LEFT JOIN, RIGHT JOIN, and FULL JOIN are equivalent to LEFT OUTER JOIN, RIGHT OUTER
JOIN, and FULL OUTER JOIN, respectively.

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Table
store_name Sales Date
Los Angeles $1500 Jan-05-1999
San Diego
Los Angeles
Boston
$250
$300
$700
Jan-07-1999
Jan-08-1999
Jan-08-1999
Table
region_name
East
East
West
West store_name
Boston
New York
Los Angeles
San Diego and we want to use a subquery to find the sales of all stores in the West region.
To do so, we use the following SQL statement:
SELECT SUM(Sales) FROM Store_Information
WHERE Store_name IN
(SELECT store_name FROM Geography
WHERE region_name = 'West')
SUM(Sales)
2050
In this example, instead of joining the two tables directly and then adding up only the sales amount for stores in the West region, we first use the subquery to find out which stores are in the West region, and then we sum up the sales amount for these stores.

select 'ALTER '||OBJECT_TYPE||‘ '||OWNER||'.'||OBJECT_NAME||' compile;' from dba_objects where status='INVALID';
'ALTER'||OBJECT_TYPE||''||OWNER||'.'||OBJECT_NAME||'COMPILE;'
ALTER PROCEDURE MAXDATA.P_REPLACE_PROD compile;
ALTER PROCEDURE MAXDATA.P_SETPROTOTYPE compile;
ALTER PROCEDURE MAXDATA.UPDATE_LV10MAST compile;
ALTER PROCEDURE MAXAPP.P_COMPPROC compile;

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Originally not to be available until the Yukon release of SQL Server, Microsoft decided to release
Reporting Services early because of the customer excitement they heard. Why the excitement?
Reporting Services fills a need that many organizations are faced with —the need to build business intelligence and reporting solutions. Until now, developers were required to embed reports into their applications, or organizations were required to purchase expensive and sometimes problematic third-party reporting solutions. Now, Reporting Services offer a complete solution for distributing reports across the enterprise; enabling businesses to make decisions better and faster.
Overview of Reporting Services
Reporting Services is a scalable, secure, robust reporting solution for SQL Server. It supports the complete reporting lifecycle by including tools for report creation, execution, distribution, and management. New users can have Reporting Services installed and new reports published within a matter of hours instead of days or weeks.
Reporting Services consists of the following key components:
Report Designer : Supports the report creation phase of the report lifecycle. It is an add-on tool for any edition of Visual Studio .NET 2003, suitable for both programmers and non-programmers.
Report Server : Provides services for execution and distribution of reports.
Report Manager : A Web-based administration tool for managing the Report Server.
Report Designer
Report Designer is a Visual Studio .NET 2003 add-on and is included with Reporting Services
(see Figure A ). As the name implies, it provides developers and non-developers an intuitive tool to create sophisticated reports. Users get standard reporting functionality such as grouping, sorting, and report formatting. This should be sufficient for most reporting needs. For more advanced reports, the Report Designer has full VB.NET support. Plus, designers can add ActiveX controls to their reports to create rich, live, interactive reports.

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One of the more compelling features of Report Designer is the ability to have dynamic, querybased parameters. This eliminates the administrator having to maintain parameter lists for all the reports (i.e., department names, office locations, employee names, etc.). You simply have to create a new dataset and tie the results to the parameter. It even allows cascading parameters.
At the heart of Reporting Services architecture is the Report Definition Language (RDL), which is an XML-based standard for defining reports. RDL is key to the Reporting Services success by allowing third parties to publish reports to the Reporting Server. There are already product offerings from independent software vendors (ISVs) today.
Though Reporting Services requires SQL Server as its repository, Report Designer can connect to all types of data sources including OLE DB, ODBC, Oracle, SQL Server, and others. It also has many rendering options such as HTML, Microsoft Excel, PDF, CSV, XML, and others. The list can also be extended by third parties or by using the Reporting Services extension library.
Report Server
The Report Server provides the repository, management, execution, and delivery functions. It is scalable and secure, and can support the most demanding reporting needs. It consists of several subcomponents, including:
Request Handler : Handles all inbound server requests and routes them to the appropriate component.
Scheduling and Delivery Processor : Provides the scheduling and delivering functionality, and it can be extended to deliver reports to other devices such as fax machines or printers.
Report Processor : Provides the execution functionality and it, too, can be extended to render to new output formats such as a Microsoft Word document.
Report Server Database : All the data required by Reporting Services is stored in the Report
Server Database, which must be a SQL Server. This includes everything from server settings to report definitions, even to cached data from a report execution.
Report Manager
Report Manager provides administrators an easy-to-use tool for configuring the server and managing the reports. Using Report Manager, administrators can configure security, change server settings, schedule reports for execution, and maintain the structure of the report folders
(see Figure B ).

Administrators have a variety of options for executing reports, including on-demand, cached reporting with an adjustable expiration period, and flexible report scheduling. All of these options are configurable at the report level through Report Manager.
Report Manager supports both push and pull distribution options. For e-mail delivery, Report Manager can include a link to the report, attach the report to the message, or embed reports directly into the message using Web archive. This eliminates one extra step for the reader of the report.
Where you need Reporting Services
Here are a few typical scenarios where Reporting Services will be invaluable:
New application development :
Most applications have reporting requirements that are sometimes very complex. With Reporting services, the business analyst, who usually has a better understanding of what is required, is able to fulfill these requirements. This frees a developer to perform other development tasks and not develop tedious, time-consuming reports. Rarely do I meet a developer who enjoys writing reports.
Furthermore, these reports will be easier to maintain and support.
Existing applications :
Because of the complexity and time required to embed reports into applications, reports are often created outside of the application using third-party tools and distributed manually or through batch jobs. By using Reporting Services, these applications can easily be extended to include a complete reporting solution, embedded within the application.

Executive dashboard
Executive dashboard is the buzzword for providing executives a comprehensive view of their business, commonly in an Enterprise Portal. Reporting Services includes several key features for an executive dashboard, such as My Reports, My Subscriptions, push/pull delivery, numerous rendering options, and support for Web services.
Though very powerful, there are a couple of scenarios that would not be suitable for Reporting
Services:
Applications using third-party reporting solutions :
Reporting Services supply only a migration tool for Microsoft Access. If you have a significant investment in another tool and it supports your needs, you’ll need to carefully consider the costs of migrating to Reporting Services.
Enterprise reporting solution :
Though non-programmers can be very productive with Report Designer, there are reporting tools absent from Report Designer that experienced report creators will miss. For example, Reporting
Services does not include a database abstraction layer to hide database details from users. This abstraction is very useful if you want to deploy a reporting solution to a large, semi-technical audience.

Whether you are writing a simple database in Access/Visual Basic or a huge clientserver web application, SQL is a powerful tool that is a must-have skill for any developer. For a beginner it is yet another skill you need to learn, but there is a shortcut that will allow you to write SQL without knowing SQL, and as a result of using these shortcuts you will actually learn to write native SQL. “So what are these shortcuts?”, I hear you cry, well, read on and find out.
All good database and report writing applications allow you to create database queries visually by deciding which tables to include, the relationship between tables, the sort order and the criteria of which records to include or not to include. Certain products (including Crystal Reports (SQL Query Designer), Microsoft Access and the very basic 'Visdata' demo that comes with Visual Basic) allow you to view this query as a native SQL statement. Be warned: Access puts lots of extra rubbish in the statement that you don't need, such as square [] and curved () brackets; it also prefixes fields with table names even if you are only using one.
So the answer to 'How do I write advanced SQL queries without knowing any SQL?' is to design your query in, say, MS-Access, click the View -> SQL View menu option, cut and paste into your own application, and hey-presto! You are an instant SQL expert!