MySql根据同一个表中的值从表中选择某些列

Question

在MySql中，如何根据我选择的某列的值来选择某些列？

"id"    "postTitle" "postBody"  "postCategory"  "postStatus"    "userId"    "userName"
"1"     "Title 1"   "Body 1"    "Alcohol"       "0"             "1"         "norman"
"2"     "Title 2"   "Body 2"    "Books"         "1"             "1"         "norman"

例如：从上表中，我尝试仅选择postTitle postStatus = 0，postTitle＆amp; postBody＆amp;如果postCategory

，则postStatus != 0

它可以解决这个问题，但这不会起作用

select if postStatus != 0 then
postTitle, postBody, postCategory
else
postTitle
End If
from tablea where id = 2;

我尝试使用大小写，但它适用于一列而不是我选择更多

select case postStatus when 1 then
postTitle, postBody
else
postTitle
End
from tablea where id = 2;

有没有办法像我尝试做的那样？

Answer 1

尝试使用UNION运算符

SELECT postTitle ,'' AS postBody ,'' AS  postCategory FROM tableName 
WHERE postStatus = '0'
UNION 
SELECT postTitle ,postBody , postCategory FROM tableName
WHERE postStatus != '0'

Answer 2

  

我尝试仅选择postTitle postStatus = 0，postTitle＆amp; postBody＆amp;如果postCategory

，则postStatus != 0

您必须使用case检查每个要显示的列。

示例：

select 
  , posttitle
  , case when poststatus = 0 then '' else postbody end as postbody
  , case when poststatus = 0 then '' else postCategory end as postCategory
from tableA where id=2;