MySQL查询字段实现字符串分割split功能的示例代码

SELECT
	SUBSTRING_INDEX( SUBSTRING_INDEX( 'a,b,c', ',', help_topic_id + 1 ), ',',- 1 ) AS num 
FROM
	mysql.help_topic 
WHERE
	help_topic_id < LENGTH( 'a,b,c' ) - LENGTH( REPLACE ( 'a,b,c', ',', '' ) ) + 1

SUBSTRING_INDEX('a,b,c',',',2)

SUBSTRING_INDEX('a,b,c',',',-2)

LENGTH('a,b,c')

replace(str,from_str,to_str)

REPLACE('a,b,c',',','、')

help_topic_id < LENGTH('a,b,c')-LENGTH(REPLACE('a,b,c',',',''))+1

SUBSTRING_INDEX(SUBSTRING_INDEX('a,b,c',',',help_topic_id+1),',',-1) AS num

CREATE DEFINER=`root`@`%` PROCEDURE `queryActualInLogic`(IN `actualPlaceId` bigint,OUT `isContain` int)
BEGIN
	DECLARE v_column VARCHAR(100);
	-- 设置终止标记
	declare done int default 0;
	
	# 查询出所有待判断的字段值集合
	declare table_loop cursor for 
		SELECT actual_place_id FROM ec_logicplace WHERE actual_place_id IS NOT NULL;
	# 捕获系统抛出的 not found 错误，如果捕获到，将 done 设置为 1  相当于try异常
	declare continue handler for not found set done=1;
	
	open table_loop;
	out_loop:LOOP
		# 遍历字段值，一一赋值
		FETCH NEXT FROM table_loop into v_column;
		IF done = 1 THEN
		    LEAVE out_loop;
		END IF;
		
		# 遍历字段值，拆分后进行判断，存在则赋值1，不存在则赋值0
		SET @STMT = CONCAT("SELECT COALESCE(count(1),0) AS isContain into @v_count FROM 
			(SELECT SUBSTRING_INDEX( SUBSTRING_INDEX( '",v_column,"' , ',', help_topic_id + 1 ), ',', -1 ) AS num 
				FROM mysql.help_topic WHERE
				help_topic_id < LENGTH( '",v_column,"' ) - LENGTH ( REPLACE ( '",v_column,"' , ',', '' ) ) + 1 
			) t WHERE t.num = ",actualPlaceId,";");
		PREPARE STMT FROM @STMT;
		#执行语句
		EXECUTE STMT;
		deallocate prepare STMT;
		
		set isContain = @v_count;
		if isContain = 1 THEN
			LEAVE out_loop;
		END IF;
		
	END LOOP out_loop;
	close table_loop;
END