关系模式Sailors(sid,lastname.firtname,age,ratring)，其中lastname允许为空. 下面哪个语句能够查找出lastname属性值不为空的水手信息. A: SELECT * FROM SAILORS WHERE LASTNAME<>’NULL’ B: SELECT * FROM SAILORS WHERE LASTNAME<>NULL C: SELECT * FROM SAILORS WHERE LASTNAME IS not NULL D: SELECT * FROM SAILORS WHERE LASTNAME not LIKE ’NULL’
关系模式Sailors(sid,lastname.firtname,age,ratring)，其中lastname允许为空. 下面哪个语句能够查找出lastname属性值不为空的水手信息. A: SELECT * FROM SAILORS WHERE LASTNAME<>’NULL’ B: SELECT * FROM SAILORS WHERE LASTNAME<>NULL C: SELECT * FROM SAILORS WHERE LASTNAME IS not NULL D: SELECT * FROM SAILORS WHERE LASTNAME not LIKE ’NULL’
1