Thanks for reply and sorry for lack of information.
What I want to know is not how to query,
but how to prevent emtpy data from being inserted in tables.
Let's say I'd like to have a table that doesn't contains any NULL value.
I'd create the table like below.
##################################
mysql> create table t (a char(10) not null);
create table t (a char(10) not null);
Query OK, 0 rows affected (0.07 sec)
mysql> insert into t values(NULL);
insert into t values(NULL);
ERROR 1048 (23000): Column 'a' cannot be null
##################################
well, looks good,
but NOT NULL only prevent NULL, as the name implied.
##################################
mysql> insert into t values('');
Query OK, 1 row affected (0.00 sec)
mysql> select * from t;
select * from t;
+---+
| a |
+---+
| |
+---+
1 row in set (0.01 sec)
###################################
Is there any easy way to implement 'NOT EMPTY' constraint?
Thank you in advance.
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