SQL Commands With Example

SQL Commands With Example

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ALTER TABLE

ALTER TABLE lets you add columns to a table in a database.

ALTER TABLE table_name ADD column_name datatype;

AND

AND is an operator that combines two conditions. Both conditions must be true for the row to be included in the result set.

SELECT column_name(s) FROM table_name WHERE column_1 = value_1 AND column_2 = value_2;

WITH

WITH clause lets you store the result of a query in a temporary table using an alias. You can also define multiple temporary tables using a comma and with one instance of the WITH keyword.

WITH temporary_name AS (SELECT FROM table_name) SELECT * FROM temporary_name WHERE column_name operator value;

WHERE

WHERE is a clause that indicates you want to filter the result set to include only rows where the following condition is true.

SELECT column_name(s) FROM table_name WHERE column_name operator value;

SELECT DISTINCT

SELECT DISTINCT specifies that the statement is going to be a query that returns unique values in the specified column(s).

SELECT DISTINCT column_name FROM table_name;

SUM

SUM() is a function that takes the name of a column as an argument and returns the sum of all the values in that column.

SELECT SUM(column_name) FROM table_name;

UPDATE

UPDATE statements allow you to edit rows in a table.

UPDATE table_name SET some_column= some_value WHERE some_column= some_value;

SELECT

SELECT statements are used to fetch data from a database. Every query will begin with SELECT.

SELECT column_name FROM table_name;

ROUND()

ROUND() is a function that takes a column name and an integer as an argument. It rounds the values in the column to the number of decimal places specified by the integer.

SELECT ROUND (column_name, integer) FROM table_name;

OUTER JOIN

An outer join will combine rows from different tables even if the join condition is not met. Every row in the left table is returned in the result set, and if the join condition is not met, then NULL values are used to fill in the columns from the right table.

SELECT column_name(s) FROM table_1 LEFT JOIN table_2 ON table_1.column_name = table_2.column_name;

MIN()

MIN() is a function that takes the name of a column as an argument and returns the smallest value in that column.

SELECT MIN(column_name) FROM table_name;

OR

OR is an operator that filters the result set to only include rows where either condition is true.

SELECT column_name FROM table_name WHERE column_name = value_1 OR column_name= value_2;

ORDER BY

ORDER BY is a clause that indicates you want to sort the result set by a particular column either alphabetically or numerically.

SELECT column_name FROM table_name ORDER BY column_name ASC | DESC;

MAX()

MAX() is a function that takes the name of a column as an argument and returns the largest value in that column.

SELECT MAX(column_name) FROM table_name;

INNER JOIN

An inner join will combine rows from different tables if the join condition is true.

SELECT column_name(s) FROM table_1 JOIN table_2 ON table_1.column_name = table_2.column_name;

IS NULL / IS NOT NULL

IS NULL and IS NOT NULL are operators used with the WHERE clause to test for empty values.

SELECT column_name(s) FROM table_name WHERE column_name IS NULL;