MySQL 在非唯一字段上的重复键

Question

我有一个包含各种参数的表格。 表的结构是:id, object_id, param_name, param_value

以下代码有效，但它附加结果而不是更新它们。 事实是我不能使用 ON DUPLICATE KEY因为我的字段是非唯一的(当然 id 除外)

INSERT INTO `params_table` (`object_id`, `param_name`, `param_value`)
SELECT
A.id AS my_object_id,
'XYZ' AS my_param_name,
IF(TMP.abc IS NULL,0,1) AS my_param_value
FROM
ref_table AS A
LEFT JOIN tmp_table AS TMP ON TMP.abc = A.abc
ON DUPLICATE KEY
UPDATE `param_value` = IF(TMP.abc IS NULL,0,1);

Answer 1

ON DUPLICATE KEY子句不仅适用于主键:

If you specify ON DUPLICATE KEY UPDATE, and a row is inserted that would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row is performed

因此，除非我遗漏了一些明显的东西，否则您只需要在要使其唯一的列组合上创建一个唯一索引:

ALTER TABLE params_table
ADD UNIQUE unique_object_param(object_id,param_name);