字符型字段，值为空，如何用SQL语句判断此字段值为空？

[skytears]

字符型字段，值为空，如何用SQL语句判断此字段值为空？

[bzszp]

select * from tbname where colname is null;

[bzszp]

只包含空格的
select * from tbname where trim(colname) is null;

[LGQDUCKY]

ORACLE不管什么字段类型，在SQL语句判断NULL都是

colname is null或colname is not null

[zhaokeke2004]

select * from tbname where colname is null
select * from tbname where colname is not null

[dinya2003]

select * from tbname where trim(colname) is null;

这应该是包含那些是NULL的记录和包含有若干空格的的记录

[ITpassport]

select * from table where Trim(colname) is null;
select * from table where Trim(colname) is not null;
select * from table where Trim(colname)='';
select * from table where Trim(colname) is nothing;