MySQL元数据操作：查询 MySQL 空表，拥有某字段的表，等

1、查询MySQL库下所有表名，数据不为空的表，反之查询为空的表

SELECT
    table_name,
    table_rows
FROM
    information_schema. TABLES
WHERE
    table_schema = 'ahbo'
AND table_rows < 1;

 

2、查询指定库拥有某字段的表

SELECT DISTINCT
    TABLE_NAME
FROM
    information_schema. COLUMNS
WHERE
    COLUMN_NAME = 'columnName'
AND TABLE_SCHEMA = 'dbName'
AND TABLE_NAME NOT LIKE 'vw%';

3、修改指定数据库中所有varchar类型的表字段的字符集为UTF8，并将排序规则修改为utf8_general_ci

SELECT CONCAT('ALTER TABLE `', table_name, '` MODIFY `', column_name, '` ', DATA_TYPE, '(', CHARACTER_MAXIMUM_LENGTH, ') CHARACTER SET UTF8 COLLATE utf8_general_ci', (CASE WHEN IS_NULLABLE = 'NO' THEN ' NOT NULL' ELSE '' END), ';')
别名
FROM information_schema.COLUMNS
WHERE TABLE_SCHEMA = 'SchoolUserOnline_20170416'
AND DATA_TYPE = 'varchar'
AND
(
    CHARACTER_SET_NAME != 'utf8'
    OR
    COLLATION_NAME != 'utf8_general_ci'
);

4、修改指定数据库中所有数据表的字符集为UTF8，并将排序规则修改为utf8_general_ci

SELECT CONCAT('ALTER TABLE ', table_name, ' CONVERT TO CHARACTER SET  utf8 COLLATE utf8_unicode_ci;')
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'databaseName'