coding++ ：MySQL 使用 SQL 语句查询数据库所有表注释已经表字段注释

1、要查询数据库 "mammothcode" 下所有表名以及表注释

/* 查询数据库 ‘mammothcode’ 所有表注释 */
SELECT TABLE_NAME,TABLE_COMMENT FROM information_schema.TABLES WHERE table_schema='mammothcode';

2、要查询表字段的注释

/* 查询数据库 ‘mammothcode’ 下表 ‘t_adminuser’ 所有字段注释 */
SELECT COLUMN_NAME,column_comment FROM INFORMATION_SCHEMA.Columns WHERE table_name='t_adminuser' AND table_schema='mammothcode'

3、一次性查询数据库 "mammothcode" 下表注释以及对应表字段注释

SELECT t.TABLE_NAME,t.TABLE_COMMENT,c.COLUMN_NAME,c.COLUMN_TYPE,c.COLUMN_COMMENT
FROM information_schema.TABLES t,INFORMATION_SCHEMA.Columns c
WHERE c.TABLE_NAME=t.TABLE_NAME AND t.`TABLE_SCHEMA`='mammothcode'

扩展：使用存储过程，对上面sql语句进行存储，SQL 如下：

DELIMITER//
DROP PROCEDURE IF EXISTS findComment//
CREATE PROCEDURE findComment (dbName VARCHAR(50))
BEGIN
   DECLARE stmt VARCHAR(65535);
   #如果用户名长度大于0
   IF LENGTH(dbName)>0 THEN
     BEGIN
       SET @sqlstr=CONCAT('SELECT t.TABLE_NAME,t.TABLE_COMMENT,c.COLUMN_NAME,c.COLUMN_TYPE,c.COLUMN_COMMENT FROM information_schema.TABLES t,INFORMATION_SCHEMA.Columns c WHERE c.TABLE_NAME=t.TABLE_NAME AND t.`TABLE_SCHEMA`=','''',dbName,'''');
      END;
   ELSE
     BEGIN
      SET @sqlstr=CONCAT('SELECT ','''','数据库名不能为空','''', 'AS ','''','提示','''');
     END;
     END IF;
   PREPARE stmt FROM @sqlstr;
   EXECUTE stmt;
END//
DELIMITER ;

调用存储过程：

CALL findComment('xiyinli_test');

上面的存储过程还可以简化：在存储过程中直接查询当前使用的数据库，如下：

DELIMITER//
DROP PROCEDURE IF EXISTS findComment//
CREATE PROCEDURE findComment ()
BEGIN
   DECLARE stmt VARCHAR(65535);
   #查询当前的 use-->database
   SET @dbName=(SELECT DATABASE());
     BEGIN
       SET @sqlstr=CONCAT('SELECT t.TABLE_NAME,t.TABLE_COMMENT,c.COLUMN_NAME,c.COLUMN_TYPE,c.COLUMN_COMMENT FROM information_schema.TABLES t,INFORMATION_SCHEMA.Columns c WHERE c.TABLE_NAME=t.TABLE_NAME AND t.`TABLE_SCHEMA`=','''',@dbName,'''');
      END;
   PREPARE stmt FROM @sqlstr;
   EXECUTE stmt;
END//
DELIMITER ;

调用：

CALL findComment();

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