MySQL 选择查询值

Question

给出下表:

id   name       value
1    primary    value1
2    secudary   value1
3    primary    value1
4    secudary   value1
5    primary    value3
6    secudary   value3

我需要SELECT * FROM table_name WHERE value = "value1"

但是我不能同时从主字段和辅字段中选择信息。

我想检查是否有 SELECT * FROM table_name WHERE value = "value1"and name = "primary" 的记录 如果有记录我使用这个结果，如果没有记录我搜索SELECT * FROM table_name WHERE value = "value1"and name = "secondary"

有什么想法吗？

Answer 1

您需要声明一个变量，选择记录来加载该变量，检查它是否有值并使用 if 语句进行选择。 (我在存储过程中执行此操作)。

declare $found int;
set $found = null;
set $found= (select id FROM table_name WHERE value = "value1" and name = "primary" limit 1);

if ($found is null) then
SELECT * FROM table_name WHERE value = "value1" and name = "secundary";
else
SELECT * FROM table_name WHERE value = "value1" and name = "primary";
end if;