SQL Cheatsheet

A quick reference for common SQL commands and keywords.

Aggregate Functions

Command / Keyword	Description
`COUNT()`	Returns the number of rows.
`SUM()`	Returns the total sum of a numeric column.
`AVG()`	Returns the average value of a numeric column.
`MIN()`	Returns the smallest value of the selected column.
`MAX()`	Returns the largest value of the selected column.

Data Definition Language (DDL)

Command / Keyword	Description
`CREATE TABLE [table_name] (...)`	Creates a new table in the database.
`ALTER TABLE [table_name] ADD [column] [datatype]`	Adds a column to a table.
`DROP TABLE [table_name]`	Deletes a table.
`CREATE INDEX [index_name] ON [table_name] (column1, ...)`	Creates an index on a table.

Data Manipulation Language (DML)

Command / Keyword	Description
`INSERT INTO [table] (col1, col2) VALUES (val1, val2)`	Adds a new row to a table.
`UPDATE [table] SET [col1]=[val1] WHERE [condition]`	Modifies existing records in a table.
`DELETE FROM [table] WHERE [condition]`	Deletes existing records from a table.

Data Query Language (DQL)

Command / Keyword	Description
`SELECT [column1], [column2]`	Selects specific columns from a table.
`SELECT * FROM [table_name]`	Selects all columns from a table.
`WHERE [condition]`	Filters records based on a condition.
`ORDER BY [column] ASC\|DESC`	Sorts the result set.
`GROUP BY [column]`	Groups rows that have the same values into summary rows.
`HAVING [condition]`	Filters groups based on a condition, used with GROUP BY.

Joins

Command / Keyword	Description
`INNER JOIN`	Returns records that have matching values in both tables.
`LEFT JOIN`	Returns all records from the left table, and the matched records from the right table.
`RIGHT JOIN`	Returns all records from the right table, and the matched records from the left table.
`FULL OUTER JOIN`	Returns all records when there is a match in either left or right table.