MySQL QueriesDDL (Data definition language)

DATABASE

TABLE

Create table CREATE TABLE <table_name> (< column_name1> <datatype> [<constraint>], < column_name2> <datatype> [<constraint>],…);

Show tables list SHOW TABLES;Describe table(table structure) DESCRIBE <table_name>;Delete/Drop table DROP TABLE <table_name>;Rename table ALTER TABLE <old_table_name>

RENAME TO <new_table_name>;

COLUMN

CONSTRAINTS

Constraints

Add constraint Drop constraint

Not null ALTER TABLE <table name>MODIFY <column_name> <datatype> NOT NULL;

ALTER TABLE <table name>MODIFY <column_name> <datatype> NULL;

Unique ALTER TABLE <table name>ADD CONSTRAINT

ALTER TABLE <table name>

Add a column ALTER TABLE <table name>ADD <new_column_name> <datatype> [<constraint>];

Rename a column ALTER TABLE <table name>CHANGE <old_column_name> <new_column_name> <datatype>[<constraint>];

Delete a column ALTER TABLE <table name>DROP <column_name>;

Modify datatype or size

ALTER TABLE <table name>MODIFY <column_name> <datatype> [<constraint>];

Create database CREATE DATABASE <database_name>;Show databases list

SHOW DATABASES;

Select/Use database

USE <database_name>;

Delete/Drop database

DROP DATABASE <database_name>;

<constraint_name>UNIQUE (<column_name>);

DROP INDEX <constraint_name>;

Check ALTER TABLE <table name>ADD CONSTRAINT <constraint_name>CHECK (<column_name><condition>);

ALTER TABLE <table name>DROP CHECK <constraint_name>;

Primary key

ALTER TABLE <table name>MODIFY <column_name> <datatype>PRIMARY KEY;

ALTER TABLE <table name>DROP PRIMARY KEY;

Default ALTER TABLE <table name>ALTER <column_name>SET DEFAULT <value>;

ALTER TABLE <table name>ALTER <column_name> DROP DEFAULT;

Foreign key

ALTER TABLE <table name>ADD CONSTRAINT <constraint_name>FOREIGN KEY (<column_name> )REFERENCES <table name1> (<column_name> );

ALTER TABLE <table name>DROP FOREIGN KEY <constraint_name>;

DML (Data Manipulation language)

INSERT

Insert into all columns INSERT INTO <table_name>VALUES (<column1_value>,< column2_value>,……);

Insert into specific columns

INSERT INTO <table_name> (<column1>, <column2>,…)VALUES (<column1_value>, <column2_value>,……);

SELECT

Select all data (all rows all columns – full table)

SELECT * FROM <table_name>;

Select specific columns SELECT <column1, column2,….>FROM <table_name>;

Select all data based on condition

SELECT *FROM <table_name> WHERE <condition>;

Select data in ascending/descending order

SELECT *FROM <table_name>ORDER BY <column1><ascending/descending>;

UPDATE

Update values which satisfy condition

UPDATE <table_name> SET <column_name>=<new_value>;

Update all values of a specific column(same values for a particular column)

UPDATE <table_name>SET <column_name>=<new_value>WHERE <condition>;

DELETE

Delete specific rows based on condition

DELETEFROM <table_name>WHERE <condition>;

Clear all data of a table(delete all rows)

DELETEFROM <table_name>;

Identifiers-An Identifier is essentially a name of a database_name, table_name, column_name or constraint_name.Rules-

1. First letter must be alphabet (a-z, A-Z).2. Second and other letters can be numbers (0-9), alphabet (a-z, A-Z) and _

(underscore).3. Must not be a keyword.