Basic MySQL queries
Download as DOCX, PDF0 likes866 views
This document summarizes MySQL queries for DDL (Data Definition Language) and DML (Data Manipulation Language) operations. It describes how to create, alter, and delete databases and tables using DDL queries like CREATE DATABASE, CREATE TABLE, ALTER TABLE, DROP TABLE. It also explains how to insert, select, update, and delete data from tables using DML queries like INSERT, SELECT, UPDATE, DELETE. Basic syntax and examples are provided for each type of query.
![MySQL Queries
DDL (Data definition language)
DATABASE
TABLE
Create database CREATE DATABASE<database_name>;
Show databases list SHOW DATABASES;
Select/Use database USE<database_name>;
Delete/Drop database DROP DATABASE<database_name>;
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>;
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><datat
ype>[<constraint>];
Delete a column ALTER TABLE <table name>
DROP <column_name>;
Modify datatype or
size
ALTER TABLE <table name>
MODIFY <column_name><datatype>
[<constraint>];
COLUMN
CONSTRAINTS
Constrain
ts
Add constraint Drop constraint
Not null ALTER TABLE <table name>
MODIFY <column_name><datatype>NOT
NULL;
ALTER TABLE <table name>
MODIFY
<column_name><datatype>NUL](https://image.slidesharecdn.com/basicmysqlqueries-130226125555-phpapp02/85/Basic-MySQL-queries-1-320.jpg)
Basic MySQL queries
- 1. MySQL Queries DDL (Data definition language) DATABASE TABLE Create database CREATE DATABASE<database_name>; Show databases list SHOW DATABASES; Select/Use database USE<database_name>; Delete/Drop database DROP DATABASE<database_name>; 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>; 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><datat ype>[<constraint>]; Delete a column ALTER TABLE <table name> DROP <column_name>; Modify datatype or size ALTER TABLE <table name> MODIFY <column_name><datatype> [<constraint>]; COLUMN CONSTRAINTS Constrain ts Add constraint Drop constraint Not null ALTER TABLE <table name> MODIFY <column_name><datatype>NOT NULL; ALTER TABLE <table name> MODIFY <column_name><datatype>NUL
- 2. DML (Data Manipulation language) INSERT Insert into all columns INSERT INTO <table_name> VALUES(<column1_value>,< column2_value>,……); Insert into specific columns INSERTINTO<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>; L; Unique ALTER TABLE <table name> ADD CONSTRAINT <constraint_name> UNIQUE (<column_name>); ALTER TABLE <table 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>;
- 3. DELETE Delete specific rows based on condition DELETE FROM <table_name> WHERE <condition>; Clear all data of a table(delete all rows) DELETE FROM <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.