SQL Cheat Sheet: CREATE TABLE, ALTER, DROP, TRUNCATE

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SQL Cheat Sheet: CREATE TABLE, ALTER, DROP, TRUNCATE

CommandSyntaxDescriptionExample
CREATE TABLE CREATE TABLE table_name (col1 datatype optional keyword, col2 datatype optional keyword,col3 datatype optional keyword,..., coln datatype optional keyword) CREATE TABLE statement is to create the table. Each column in the table is specified with its name, data type and an optional keyword which could be PRIMARY KEY, NOT NULL, etc., CREATE TABLE employee ( employee_id char(2) PRIMARY KEY, first_name varchar(30) NOT NULL, mobile int);
ALTER TABLE - ADD COLUMN1. ALTER TABLE table_name ADD column_name_1 datatype....ADD COLUMN column_name_n datatype; 
2. ALTER TABLE table_name ADD COLUMN column_name_1 datatype....ADD COLUMN column_name_n datatype; 		ALTER TABLE statement is used to add the columns to a table.1. ALTER TABLE employee ADD income bigint;
2. ALTER TABLE employee ADD COLUMN income bigint;
ALTER TABLE - ALTER COLUMN ALTER TABLE table_name ALTER COLUMN column_name_1 SET DATA TYPE datatype;ALTER TABLE ALTER COLUMN  statement is used to modify the data type of columns.ALTER TABLE employee ALTER COLUMN mobile SET DATA TYPE CHAR(20);
ALTER TABLE - DROP COLUMN ALTER TABLE table_name DROP COLUMN column_name_1 ;ALTER TABLE DROP COLUMN  statement is used to remove columns from a table.ALTER TABLE employee DROP COLUMN mobile ;
ALTER TABLE - RENAME COLUMN ALTER TABLE table_name RENAME COLUMN current_column_name TO new_column_name;ALTER TABLE RENAME COLUMN  statement is used to rename the columns in a table.ALTER TABLE employee RENAME COLUMN first_name TO name ;
TRUNCATE TABLETRUNCATE TABLE table_name IMMEDIATE;TRUNCATE TABLE statement is used to delete all of the rows in a table. The IMMEDIATE specifies to process the statement immediately and that it cannot be undone.TRUNCATE TABLE employee IMMEDIATE ;
DROP TABLEDROP TABLE table_name ;Use the DROP TABLE statement to delete a table from a database. If you delete a table that contains data, by default the data will be deleted alongside the table.DROP TABLE employee ;

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