sybase的一个sql话语，包含datalength和substriing两个函数

sybase的一个sql语句，包含datalength和substriing两个函数

select  F_KMBH, F_KMMC, F_YSBH, F_YSMC 
from LSKMXX, CBYSZD 
where LSKMXX.F_MX = 1 and CBYSZD.F_MX = 1 and  F_KMBH like '5304%' and LSKMXX.F_SYZT = '1'
and substring(F_KMBH, 5, datalength(F_KMBH) - 4) = substring(F_YSBH, 5, datalength(F_YSBH) - 4)