例子：
实际使用SQL语句：
SELECT
`a`.`user_name` AS `user_name`,
`a`.`user_id` AS `user_id`,
`a`.`unit` AS `unit`,
`a`.`topic_id` AS `topic_id`,
`a`.`topic_name` AS `topic_name`,
substring_index( substring_index( `a`.`field4`, '^', ( `b`.`id` + 1 ) ), '^',- ( 1 ) ) AS `field4`
FROM
(
`field4_view` `a`
JOIN `for_test` `b` ON (
(
`b`.`id` < ( ( length( `a`.`field4` ) - length( REPLACE ( `a`.`field4`, '^', '' ) ) ) + 1 )
)
)
)
WHERE
(
substring_index( substring_index( `a`.`field4`, '^', ( `b`.`id` + 1 ) ), '^',- ( 1 ) ) <> ''
)
来源：/brianlai/p/13350584.html
