MySQL:用IF语句判断该插入哪个值怎么写？

insert into tablename
select 0,'123456' from tablename
where sign=1 and phone='123456';

insert into test
select 0,'123456' from test
where sign=1 and phone='123456'
union all
select distinct 1,'123456' from test
where not exists(select 1 from test where sign=1 and phone='123456');
mysql> select * from t_floodow;
Empty set (0.00 sec)mysql> insert into t_floodow
    -> select count(*)=0,'123456'
    -> from t_floodow
    -> where col1=1 and phone='123456';
Query OK, 1 row affected (0.06 sec)
Records: 1  Duplicates: 0  Warnings: 0-- 第一次，不存在 1,123456, 所以插入 |    1 | 123456 |
mysql> select * from t_floodow;
+------+--------+
| col1 | phone  |
+------+--------+
|    1 | 123456 |
+------+--------+
1 row in set (0.00 sec)mysql> insert into t_floodow
    -> select count(*)=0,'123456'
    -> from t_floodow
    -> where col1=1 and phone='123456';
Query OK, 1 row affected (0.08 sec)
Records: 1  Duplicates: 0  Warnings: 0-- 第二次，存在 1,123456, 所以插入 |    0 | 123456 |
mysql> select * from t_floodow;
+------+--------+
| col1 | phone  |
+------+--------+
|    1 | 123456 |
|    0 | 123456 |
+------+--------+
2 rows in set (0.00 sec)mysql>
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http://topic.csdn.net/u/20090501/15/7548d251-aec2-4975-a9bf-ca09a5551ba5.html