Question

我想使用条件

ON DUPLICATE KEY UPDATE

根据this question中提供的示例，假设 name 是主键。我们想执行以下查询：

INSERT INTO beautiful (name, age, col3, col 4, ..., col 100)
    VALUES
    ('Helen', 24, ...),
    ('Katrina', 21, ...),
    ('Samia', 22, ...),
    ('Hui Ling', 25, ...),
    ('Yumie', 29, ...)
ON DUPLICATE KEY UPDATE
    age = VALUES(age),
    col3= VALUES(col3),
    col4= VALUES(col4),
     ...
    col100= VALUES(col100)

并且（在MariaDB中）我希望只有当新接收的记录的年龄大于数据库中已存在的记录的年龄时才能完成更新。

有办法做到这一点吗？

更新：已更新，以反映每条记录都有多个字段

的事实

Answer 1

似乎微不足道

MariaDB [sandbox]> create table t(name varchar(20),age int default 0 , primary key(name));
Query OK, 0 rows affected (0.28 sec)

MariaDB [sandbox]>
MariaDB [sandbox]> INSERT INTO t (name, age)
    ->     VALUES
    ->     ('Helen', 24),
    ->     ('Katrina', 21),
    ->     ('Samia', 22),
    ->     ('Hui Ling', 25),
    ->     ('Yumie', 29)
    -> ON DUPLICATE KEY UPDATE
    ->     age = if(VALUES(age) > age,values(age),age);
Query OK, 5 rows affected (0.03 sec)
Records: 5  Duplicates: 0  Warnings: 0

MariaDB [sandbox]>
MariaDB [sandbox]> select * from t;
+----------+------+
| name     | age  |
+----------+------+
| Helen    |   24 |
| Hui Ling |   25 |
| Katrina  |   21 |
| Samia    |   22 |
| Yumie    |   29 |
+----------+------+
5 rows in set (0.00 sec)

MariaDB [sandbox]>
MariaDB [sandbox]> INSERT INTO t (name, age)
    ->     VALUES
    ->     ('Helen', 25),
    ->     ('Katrina', 21),
    ->     ('Samia', 22),
    ->     ('Hui Ling', 25),
    ->     ('Yumie', 29)
    -> ON DUPLICATE KEY UPDATE
    ->     age = if(VALUES(age) > age,values(age),age);
Query OK, 2 rows affected (0.02 sec)
Records: 5  Duplicates: 1  Warnings: 0

MariaDB [sandbox]>
MariaDB [sandbox]> select * from t;
+----------+------+
| name     | age  |
+----------+------+
| Helen    |   25 |
| Hui Ling |   25 |
| Katrina  |   21 |
| Samia    |   22 |
| Yumie    |   29 |
+----------+------+
5 rows in set (0.00 sec)

如果有n列在年龄变化时更新

drop table if exists t;

create table t(name varchar(20),age int default 0 , col1 int, col2 int,col3 int,primary key(name));
INSERT INTO t (name, age, col1,col2,col3)
 VALUES
      ('Helen', 24,1,1,1),
      ('Katrina', 21,1,1,1),
      ('Samia', 22,1,1,1),
      ('Hui Ling', 25,1,1,1),
      ('Yumie', 29,1,1,1)
  ON DUPLICATE KEY UPDATE
     col1 = if(VALUES(age) > age,values(col1),col1),
     col2 = if(VALUES(age) > age,values(col2),col2),
     col3 = if(VALUES(age) > age,values(col3),col3),
     age = if(VALUES(age) > age,values(age),age);

select * from t;
INSERT INTO t (name, age, col1,col2,col3)
 VALUES
      ('Helen', 25,2,2,2),
      ('Katrina', 21,2,2,2),
      ('Samia', 22,1,1,1),
      ('Hui Ling', 25,1,1,1),
      ('Yumie', 29,1,1,1)
  ON DUPLICATE KEY UPDATE
      col1 = if(VALUES(age) > age,values(col1),col1),
     col2 = if(VALUES(age) > age,values(col2),col2),
     col3 = if(VALUES(age) > age,values(col3),col3),
     age = if(VALUES(age) > age,values(age),age);

select * from t;

MariaDB [sandbox]> select * from t;
+----------+------+------+------+------+
| name     | age  | col1 | col2 | col3 |
+----------+------+------+------+------+
| Helen    |   25 |    2 |    2 |    2 |
| Hui Ling |   25 |    1 |    1 |    1 |
| Katrina  |   21 |    1 |    1 |    1 |
| Samia    |   22 |    1 |    1 |    1 |
| Yumie    |   29 |    1 |    1 |    1 |
+----------+------+------+------+------+
5 rows in set (0.00 sec)

注意年龄必须上次更新。键入所有可更新列没有快捷方式。如果除了age之外的列是动态的，那么可能值得查看动态sql。另一种方法可能是使用触发器将插入加载到临时表以更新主表。

MySQL / MariaDB ON DUPLICATE KEY UPDATE基于条件

1 个答案: