Question

我有一个问题：

select
p.id AS id,
p.text AS text,
p.date AS date,
k.color AS color,
...

FROM

cform_mba_contacts p,
cform_mba_contacts_category_links o,
cform_mba_contacts_status k,
...

where

p.id_peoples = ".$this->id." AND
o.id_contacts = p.id AND
o.id_status = k.id AND
...

order by p.date

此查询在引入新条件之前完美运行。我需要选择具有和条件且仅使用p.id_peoples = ".$this->id."的数据。我试图使用UNION，但这不起作用。我怎么能这样做？

更新

我通过阅读有关UNION运算符的其他文档来解决我的问题在order子句中需要使用not p.date而不是date，而在second语句中需要选择在第一个语句中选择的列数

Answer 1

也许你想要的是 UNION ALL 。

Answer 2

我认为你正在寻找这个：

WHERE 1 = 1
AND (@id IS NULL 
     OR 
     ( p.id_peoples = @id  
       AND o.id_contacts = p.id 
       AND o.id_status = k.id
     ))

ORDER BY p.date

@id是.$this->id.传递的参数。

仅当o.id_contacts = p.id AND o.id_status = k.id传递的参数不为空时，才会应用条件.$this->id.。

Answer 3

试试这个：

WHERE  p.id_peoples <> ".$this->id." 
       OR ( o.id_contacts = p.id AND
            o.id_status = k.id AND
            ...
          )

Answer 4

create a string and execute the string at the last.

decalre @thequery varchar(max);
 set @thequery ='select * from emp'
if (1=1)
begin
set @thequery = @thequery + ' where emp_id =1'
end
else
begin
set @thequery = @thequery + ' where emp_id=0'
 end exec("@thequery ");

WHERE子句中的IF条件

4 个答案: