MySQL/MariaDB ON DUPLICATE KEY UPDATE 基于条件

Question

我想使用条件

重复密钥更新

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

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）我希望更新完成，只有当新收到的记录的年龄大于数据库中已经存在的记录时。

有没有办法做到这一点？

更新：更新以反映每条记录都有多个字段

Answer 1

看似微不足道

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，那么

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)

笔记年龄必须最后更新。没有快捷键可以键入所有可更新的列。如果年龄以外的列是动态的，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中以更新主表。