LAB #3
QUERYING DATA
Delete and update
 Delete a record
DELETE
FROM vet_appt
WHERE vet_appt_id = 3;
 Update a record
UPDATE animal
SET’ gender = “MS”
WHERE animal_id = 3
What would happen if you didn’t include a where clause
with a delete or update record command?
2
Query Data From Database
 We use the SELECT statement to retrieve
information from the database.
SELECT attribute/s
FROM table/s
WHERE (condition)
Simple Select
List all the record s (rows) and all attributes
(columns) in table:
* - WILDCARD
SELECT * FROM tableName;
Select * from animal
Select Attributes/Fields
SELECT fieldNameA, fieldNameB
FROM tableName;
The order in which you list the attributes will be the
order the attributes are displayed.
SELECT flname, ffname
FROM faculty;
SELECT ffname, flname
FROM faculty;
Select Distinct
SELECT sclass
FROM student;
SC
-SR
SR
JR
SO
SO
FR
SELECT DISTINCT sclass
FROM student;
SC
-SR
JR
SO
FR
Filtering Data:
Clause
The WHERE
SELECT fieldName FROM tableName
WHERE fieldName [some condition];
 Returns only those records that match the
condition
Example 1: Number
SELECT sfname, slname, fid
FROM student
WHERE fid = 1;
Example 2: String
SELECT sfname, slname
FROM student
WHERE sclass= 'SO';
Remember
Values in strings are
Case sensitive
Comparison Operators …
A and B - Intersect
A OR B –UNION: all of
A (including yellow,
gray and purple) all of B
(including aqua, and
purple and gray)
C and B
12
Logical Operators - OR
SELECT fieldNameA, fieldNameB
FROM tableName
WHERE attribute = X or attribute = Y;
Must match EITHER
Select client_fname, client_lname, add1, city, state, zip
From vet_client
Where state = ‘NJ’ OR state = ‘PA’ ;
Arithmetic Operators – Rules
of Precedence
 Arithmetic operators and rules of precedence
Table 5.5
14
Logical Operators – AND
SELECT fieldNameA, fieldNameB
FROM tableName
WHERE attribute = X AND attribute = Y;
Must match BOTH
Select client_fname, client_lname, add1, city, state, zip
From vet_client
Where state = ‘NJ’ AND state= ‘PA’ ;
Would this work?
Logical Operators – AND
Select client_fname, client_lname, add1, city,
state, zip
From vet_client
Where city= ‘Philadelphia’ AND state= ‘PA’ ;
Comparison Operators
Symbol
>
>=
<
<=
!=, <>
IN
Description
Greater Than
Greater than or equal to
Less Than
Less than or equal to
Not equal to
Looks for records with a value which is
equal to one of the values in a list
BETWEEN Looks for records with a value between
two different values
EXAMPLES of Comparison
Operator
SELECT appt_date, appt_type,
temperature
FROM vet_appt
WHERE (temperature >= 102 ;
SELECT appt_date, appt_type,
temperature
FROM vet_appt
WHERE appt_type in (1, 2, 3)’
Logical Operators – AND
SELECT fieldNameA, fieldNameB
FROM tableName WHERE criteria
Select client_fname, client_lname, add1, city, state,
zip
From vet_client
Where state = ‘NJ’ AND fieldNameA = ‘PA’ ;
Would this work?
Wildcard Characters
_ : 1 character %: multiple characters
SELECT client_lname
FROM vet_client
WHERE client_lname LIKE ‘_emple’;
SELECT client_lname
FROM vet_client
WHERE client_lname LIKE ‘%d%
NULL/NOT NULL Operator
SELECT student_fname, student_lname,
FROM student
WHERE student_mname IS NULL
SELECT student_fname, student_lname,
FROM student
WHERE student_mname IS NOT NULL
Sorting the Output: ORDER BY
SELECT client_lname, client_fname
ORDER BY client_lname desc;
Can Nest order
ASC is default
Example:
SELECT bldg_code, room, capacity
FROM location WHERE capacity >= 40
ORDER BY capacity DESC, bldg_code ASC ;
BLDG_CODE
ROOM
CAPACITY
-------------------------------------------------------SP
101
150
BUS
211
55
BUS
105
42
SP
202
40
To Summarize
SELECT (distinct)
fieldName/s
FROM
tableName
WHERE
fieldName [some condition]
ORDER BY
fieldName ASC/DESC;