式例：
SELECT
hcc.APPLY_DATE,
substring_index( substring_index( hcc.CHANGE_TYPE, ',', b.help_topic_id + 1 ), ',', - 1 ) CHANGE_TYPE,
hcc.CHANGE_CONTENT
FROM
hps_so_line hsl
INNER JOIN hps_so_head hsh ON ( hsh.SO_HEAD_ID = hsl.SO_HEAD_ID AND hsh.TENANT_ID = hsl.TENANT_ID )
INNER JOIN hps_conctract_change hcc ON ( hsh.SO_HEAD_ID = hcc.SO_HEAD_ID AND hsh.TENANT_ID = hcc.TENANT_ID )
INNER JOIN mysql.help_topic b ON (
b.help_topic_id < ( LENGTH( hcc.CHANGE_TYPE ) - LENGTH( REPLACE ( hcc.CHANGE_TYPE, ',', '' )) + 1 ))
WHERE
1 = 1
