6.5也有DATALENGTH函数
DATALENGTH ('expression')
The actual length of an expression of any datatype. Because varchar, varbinary, text, and image datatypes can store variable-length data, DATALENGTH is especially useful with those datatypes. The DATALENGTH of any null data returns NULL. For all other datatypes, DATALENGTH reports their defined length (because NON NULL fixed-width character data is always right-padded with spaces).