过程执行后会随机从表中筛选指定数目的记录返回。过程包含三个参数，分别是表名，行数和主键id。过程只支持int类型单主键的表。主键可以省略为空，这样过程会自动查找主键，不过这样比较慢。 MySQL CREATE DEFINER=`root`@`%` PROCEDURE `rand_data`(IN `tbN
过程执行后会随机从表中筛选指定数目的记录返回。过程包含三个参数，分别是表名，行数和主键id。过程只支持int类型单主键的表。主键可以省略为空，这样过程会自动查找主键，不过这样比较慢。MySQL
CREATE DEFINER=`root`@`%` PROCEDURE `rand_data`(IN `tbName` VARCHAR(50), IN `rowCnt` INT, IN `tbKey` VARCHAR(50))
LANGUAGE SQL
NOT DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT '随机获取若干记录,只适用于单主键表'
BEGIN
#获取主键名
IF tbKey IS NOT NULL THEN
SET @tbKey=tbKey;#参数里面已经有，这种情况比较快
ELSE
#参数里面没，从系统表查找主键，比较耗时
SELECT @tbKey:=c.COLUMN_NAME
FROM
INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS t,
INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS c
WHERE
t.TABLE_NAME = c.TABLE_NAME
AND t.TABLE_SCHEMA = c.TABLE_SCHEMA
AND t.TABLE_SCHEMA = database()
AND t.TABLE_NAME = tbName
AND t.CONSTRAINT_TYPE = 'PRIMARY KEY';
END IF;
#获取最大id,最小id和记录数
SET @getMaxIdSql = CONCAT('SELECT @maxId:=MAX(', @tbKey, '),',
'@minId:=MIN(', @tbKey, '),',
'@totalCnt:=COUNT(', @tbKey, ')',
' FROM `', tbName, '`;');
PREPARE getMaxId FROM @getMaxIdSql;
EXECUTE getMaxId;
DEALLOCATE PREPARE getMaxId;
#创建临时表
DROP TABLE IF EXISTS rand_tt;
SET @temTbSql = CONCAT('CREATE TEMPORARY TABLE rand_tt SELECT 0 aid,tb.* FROM `',tbName,'` tb LIMIT 0;');
PREPARE temTb FROM @temTbSql;
EXECUTE temTb;
DEALLOCATE PREPARE temTb;
#构建获取一条记录的sql
SET @randRowSql = CONCAT('INSERT INTO rand_tt SELECT @cnt:=@cnt+1 aid,tb.* FROM ',
tbName, ' tb WHERE tb.', @tbKey, '=?;');
PREPARE addRow FROM @randRowSql;
#生成随机记录
SET @cnt=0;
insertLoop: LOOP
SET @id=FLOOR(RAND()*(@maxId-@minId)+@minId);
IF NOT EXISTS (SELECT id FROM rand_tt WHERE id=@id) THEN
EXECUTE addRow USING @id;
IF @cnt >= rowCnt OR @cnt >= @totalCnt THEN
LEAVE insertLoop;
END IF;
END IF;
END LOOP insertLoop;
DEALLOCATE PREPARE addRow;
#返回数据
ALTER TABLE rand_tt DROP COLUMN aid;
SELECT * FROM rand_tt;
END
