Question

我想在PostgreSQL中使用CASE语句进行插入。

如果我的结果集的计数等于零，我正在尝试插入。如果它不等于零，那么我只想在该表上选择最大时间。

select
    case
        when (select count(*) from x where TableName = 'p' ) > 0
              then
             (select    MaxDataDate from    x where TableName = 'p' ) 
        when (select count(*) from s where TableName = 'p') = 0
              then
             (insert into x values('p','1900-01-01'))
end

Answer 1

可以像data-modyfying CTE一样翻译成纯SQL：

WITH sel AS (SELECT maxdatadate FROM x where tablename = 'p')
,    ins AS (
    INSERT INTO x (?column_name1?, ?column_name2?)
    SELECT 'p'::?type1?, '1900-01-01'::?type2?
    WHERE  NOT EXISTS (SELECT 1 FROM ins)
    AND    EXISTS (SELECT 1 FROM s WHERE tablename = 'p')
    )
SELECT * FROM ins;

填写缺失的信息。 ?标志着这些景点。

假设x.tablename是唯一的。否则，您的第二个SELECT声明将是无意义的。

替代方案是plpgsql函数或DO语句like @X.L.Ant already hinted in his comment.

中的程序解决方案

CASE语句中的条件INSERT或SELECT

1 个答案: