如下一张表:
a = "a" NULL "b" b = 1 2 3 t = table(a, b)
a列的数据类型是string,我想找出a中为空值的列,SQL语句如下:
select * from t where a = NULL
但是失败了,报错信息如下,请问正确SQL语句应该如何写:
Both arguments for character comparison must have the category of LITERAL
可以进行空值数据类型的转换,例子如下:
select * from t where a=string(NULL)
结果: