MySQL information_ Schema database

Preface

information_schema database , This database contains mysql Metadata , Include database information 、 Information of tables in database, etc . Therefore, you can query the disk space occupied by the database by information_schema Database operation .

Introduction to main tables

• schemata surface ： This table is mainly stored in mysql Information for all databases in
• tables surface ： This table stores the information of all tables in the database , Include information such as how many columns each table has .
• columns surface ： This table stores the table field information in all tables .
• statistics surface ： Stored information of indexes in the table .
• user_privileges surface ： The user's permission information is stored .
• schema_privileges surface ： Database permissions stored .
• table_privileges surface ： Stored table permissions .
• column_privileges surface ： The permission information of the column is stored .
• character_sets surface ： Store mysql Information about available character sets .
• collations surface ： Provides cross reference information for each character set .
• collation_character_set_applicability surface ： amount to collations Table and character_sets A comparison of the first two fields of the table , The cross reference information between character sets is recorded .
• table_constraints surface ： This table is mainly used to record the tables with constraints and the constraint types .
• key_column_usage surface ： Record columns with constraints .
• routines surface ： Records information about stored procedures and functions , Does not contain custom procedure or function information .
• views surface ： Recorded view information , Need to have show view jurisdiction .
• triggers surface ： Stored trigger information , Need to have super jurisdiction .

Application example

Query the column information of all tables under the specified database （ Including index ）

 select 
    tbst.table_schema,
    tbst.table_name,
    tbst.ordinal_position,
    tbst.COLUMN_NAME,
    tbst.COLUMN_TYPE,
    tbst.DATA_TYPE,
    tbst.IS_NULLABLE,
    tbst.COLUMN_COMMENT,
    tbix.INDEX_NAME
    FROM 
    (SELECT 
    table_schema,
    table_name,
    ordinal_position,
    COLUMN_NAME,
    COLUMN_TYPE,
    DATA_TYPE,
    IS_NULLABLE,
    COLUMN_COMMENT 
    FROM INFORMATION_SCHEMA.COLUMNS 
    WHERE table_schema = '%s'
    and TABLE_NAME not in('DATABASECHANGELOG', 'DATABASECHANGELOGLOCK')
    ) tbst
     SELECT 
    table_schema,
    table_name,
    ordinal_position,
    COLUMN_NAME,
    COLUMN_TYPE,
    DATA_TYPE,
    IS_NULLABLE,
    COLUMN_COMMENT 
    FROM INFORMATION_SCHEMA.COLUMNS 
    WHERE table_schema = '%s'
    and TABLE_NAME not in('DATABASECHANGELOG', 'DATABASECHANGELOGLOCK')
    ) tbst
    left join
    (
    select 
    TABLE_SCHEMA, 
    TABLE_NAME, 
    INDEX_NAME, 
    GROUP_CONCAT(COLUMN_NAME) as INDEX_COLUMN
    from
    information_schema.statistics
    where table_schema='%s' 
    and TABLE_NAME not in('DATABASECHANGELOG', 'DATABASECHANGELOGLOCK')
    GROUP BY TABLE_NAME, INDEX_NAME
    ) tbix
    ON  tbst.table_name = tbix.TABLE_NAME 
    AND tbst.COLUMN_NAME = tbix.INDEX_COLUMN
    AND tbst.table_schema = tbix. TABLE_SCHEMA
    ORDER BY table_name, ordinal_position;

Query the engine and character set of all tables under the specified database

select 
TABLE_SCHEMA,
TABLE_NAME,
ENGINE,
TABLE_ROWS,
TABLE_COLLATION,
left(TABLE_COLLATION,7) as TABLE_COLLATION_SHORT
from information_schema.tables s
where table_schema='%s'
and TABLE_NAME not in('DATABASECHANGELOG', 'DATABASECHANGELOGLOCK');

Capacity of the table to query

Add up the data and index of the table , 　　 The result obtained above is in bytes , You can divide by two 1024 To the M Results in units .

select sum(DATA_LENGTH)+sum(INDEX_LENGTH) from information_schema.tables 
where table_schema=' Database name ';

Reference documents

1. https://www.cnblogs.com/diandiandidi/p/5582309.html