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SQL Cheat Sheet: FUNCTIONS and Implicit
JOIN
Command
Syntax
COUNT
SELECT COUNT(column_name)
FROM table_name WHERE
condition;
AVG
SELECT AVG(column_name) FROM
table_name WHERE condition;
SUM
SELECT SUM(column_name) FROM
table_name WHERE condition;
MIN
SELECT MIN(column_name) FROM
table_name WHERE condition;
MAX
SELECT MAX(column_name) FROM
table_name WHERE condition;
ROUND
SELECT ROUND(2number,
decimals, operation) AS
RoundValue;
LENGTH(column_name)
LENGTH SELECT
FROM table;
UCASE
SELECT UCASE(column_name)
FROM table;
DISTINCT(column_name)
DISTINCT SELECT
FROM table;
DAY
Description
Example
COUNT function returns the
COUNT(dep_id) FROM
number of rows that matches a SELECT
employees;
specified criterion.
AVG function returns the
SELECT AVG(salary) FROM
average value of a numeric
employees;
column.
SUM function returns the total
SELECT SUM(salary) FROM
employees;
sum of a numeric column.
MIN function returns the
SELECT MIN(salary) FROM
smallest value of the
employees;
SELECTed column.
MAX function returns the largest
SELECT MAX(salary) FROM
value of the SELECTed
employees;
column.
ROUND function rounds a
ROUND(salary) FROM
number to a specified number SELECT
employees;
of decimal places.
LENGTH function returns the
SELECT LENGTH(f_name) FROM
employees;
length of a string (in bytes).
UCASE function that displays the
UCASE(f_name) FROM
column name in each table in SELECT
employees;
uppercase.
DISTINCT function is used to
SELECT
display data without
DISTINCT(UCASE(f_name)) FROM
employees;
duplicates.
SELECT DAY(column_name) FROM DAY function returns the day
table
the month for a given date
DAY(b_date) FROM
of SELECT
employees where emp_id =
'E1002';
is used to display SELECT YEAR(CURRENT DATE CURRENT SELECT (CURRENT DATE the current date.This can be
b_date) As AGE,
COLUMN) FROM table;
DATE
subtracted from the previous CURRENT_DATE, b_date FROM
employees;
date to get the difference.
SELECT emp_id, fmame, lname,
Subquery SELECT column_name [,
Subquery is a query within
column_name ] FROM table1 [, another SQL query and
salary
table2 ] WHERE column_name
employees
embedded within the WHERE FROM
OPERATOR (SELECT column_name
where salary
[, column_name ] FROM table1 clause.
< (SELECT AVG(salary)
CURRENT DATE
[, table2 ] [WHERE])
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A subquery is used to return
data that will be used in the
FROM employees);
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main query as a condition to
further restrict the data to be
retrieved.
SELECT * FROM ( SELECT
emp_id, f_name, l_name,
dep_id FROM employees) AS
emp4all;
SELECT * FROM employees
WHERE job_id IN (SELECT
job_ident FROM jobs);
combines
the two or more records but
displays only matching values SELECT * FROM employees,
jobs where employees.job_id
in both tables. Inner join
= jobs.job_ident;
applies only the specified
columns.
Implicit Cross Join defines
as a Cartesian product where
SELECT * FROM employees,
the number of rows in the first jobs;
table multiplied by the number
of rows in the second table..
Implicit Inner Join
SELECT column_name(s) FROM
Implicit
table1, table2 WHERE
Inner Join table1.column_name =
table2.column_name;
Implicit
SELECT column_name(s) FROM
Cross Join table1, table2;
Author(s)
Lakshmi Holla
Changelog
Date
Version Changed by Change Description
2023-05-04 1.1
Benny Li
Formatting changes
2021-07-28 1.0
Lakshmi Holla Initial Version
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