如何更新和插入 MySQL 中的特定条件？

Question

我有一个table名字'test':

create table test(main_mix_number varchar(20),formulation_mix_number varchar(20),param1 varchar(20),param2 varchar(20));

它有以下行：

insert into test(formulation_mix_number,param1,param2) values ('101A','abc','xyz');
+-----------------+------------------------+--------+--------+
| main_mix_number | formulation_mix_number | param1 | param2 |
+-----------------+------------------------+--------+--------+
| NULL            | 101A                   | abc    | xyz    |
+-----------------+------------------------+--------+--------+

现在，

if number of row where 'main_mix_number' is 'NULL' equals 1 then I want to update the row 

else if number of rows where 'main_mix_number' is 'NULL' greater than 1 then I want to update the first row 

else if number of rows where 'main_mix_number' is 'NULL' equals 0 then row insertion took place.

所以，我尝试了以下查询：

    select (
case when (select count(distinct(formulation_mix_number)) from test where formulation_mix_number='101A' and main_mix_number is NULL)=1 then 
(update test set main_mix_number='1A' where formulation_mix_number='101A') 
when (select count(distinct(formulation_mix_number)) from test where formulation_mix_number='101A' and main_mix_number is NULL)>1 then 
(update test set main_mix_number='1A' where formulation_mix_number='101A' order by formulation_mix_number desc limit 1) 
when (select count(distinct(formulation_mix_number)) from test where formulation_mix_number='101A' and main_mix_number is NULL)=0 then 
(insert into test (main_mix_number,formulation_mix_number,param1,param2) 
select * from (select '1A' as main_mix_number,'101A' as fromulation_mix_number,param1,param2 from test where formulation_mix_number='101A' order by fromulation_mix_number desc limit 1) as tmp 
where not exists (select main_mix_number,formulation_mix_number from test where main_mix_number='1A' and formulation_mix_number='101A')) else NULL end) 
from temp;

但是由于 select 和更新或插入不能一起工作，所以这个查询不起作用。我知道还有另一种方法可以将 formulation_mix_number 和 main_mix_number 保存在单独的 table 中，并且不要将 main_mix_number 与 formulation_mix_number 细节混在一起。但是由于某些原因，我不允许在我的数据库中添加另一个 table。

Answer 1

这需要动态 sql

create table test(main_mix_number varchar(20),formulation_mix_number varchar(20),param1 varchar(20),param2 varchar(20));

insert into test(formulation_mix_number,param1,param2) values ('101A','abc','xyz');

    SELECT 
    (CASE
        WHEN
            (SELECT 
                    COUNT(DISTINCT (formulation_mix_number))
                FROM
                    test
                WHERE
                    formulation_mix_number = '101A'
                        AND main_mix_number IS NULL) = 1
        THEN
            (@sql:='update test set main_mix_number=\'1A\' where formulation_mix_number=\'101A\'')
        WHEN
            (SELECT 
                    COUNT(DISTINCT (formulation_mix_number))
                FROM
                    test
                WHERE
                    formulation_mix_number = '101A'
                        AND main_mix_number IS NULL) > 1
        THEN
            (@sql:='update test set main_mix_number=\'1A\' where formulation_mix_number=\'101A\' order by formulation_mix_number desc limit 1')
        WHEN
            (SELECT 
                    COUNT(DISTINCT (formulation_mix_number))
                FROM
                    test
                WHERE
                    formulation_mix_number = '101A'
                        AND main_mix_number IS NULL) = 0
        THEN
            (@sql:='insert into test (main_mix_number,formulation_mix_number,param1,param2) 
            select * from (select \'1A\' as main_mix_number,\'101A\' as fromulation_mix_number,param1,param2 from test where formulation_mix_number=\'101A\' order by fromulation_mix_number desc limit 1) as tmp 
            where not exists (select main_mix_number,formulation_mix_number from test where main_mix_number=\'1A\' and formulation_mix_number=\'101A\')')
        ELSE NULL
    END)
FROM
    test

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE stmt;

SELECT * FROM test

main_mix_number | formulation_mix_number | param1 | param2
:-------------- | :--------------------- | :----- | :-----
1A              | 101A                   | abc    | xyz

db<>fiddle here

如何更新和插入 MySQL 中的特定条件？

how to update and insert on specific condition in MySQL?

mysql

sql

dml