[英]MySQL IF statement on a calculated column
How can I use a calculated column in an SQL statement that uses an 'IF'Statement in the 'Where' clause. 如何在SQL语句中使用计算列,该语句在“ Where”子句中使用“ IF”语句。
My query is down below. 我的查询在下面。 I keep getting the error
我不断收到错误
Unknown column 'e_owner_id_church' in 'where clause'
SELECT idu,fname,lname,id_file,friendly_name,file_name,uploaded_by,date_uploaded,
file_last_modified,owner_id,
CASE WHEN owned_by='church' THEN church_name WHEN owned_by='user' THEN CONCAT(fname, ' ', lname) END AS e_owner_name,
CASE WHEN owned_by='church' THEN id_church END AS e_owner_id_church,
CASE WHEN owned_by='user' THEN idu END AS e_owner_id_user
FROM files,file_affiliations,churches,users
WHERE owner_id=IF(e_owner_id_church != null, e_owner_id_church, e_owner_id_user)
GROUP BY file_id
This could work as a workaround using HAVING
clause: 使用
HAVING
子句可以解决此问题:
SELECT idu
, fname
, lname
, id_file
, friendly_name
, file_name
, uploaded_by
, date_uploaded
, file_last_modified
, owner_id
, CASE owned_by
WHEN 'church' THEN church_name
WHEN 'user' THEN CONCAT(fname, ' ', lname)
END AS e_owner_name
, CASE owned_by
WHEN 'church' THEN id_church
ELSE NULL
END AS e_owner_id_church
, CASE owned_by
WHEN 'user' THEN idu
ELSE NULL
END AS e_owner_id_user
FROM files
, file_affiliations
, churches
, users
GROUP BY file_id
HAVING owner_id = IFNULL(e_owner_id_church, e_owner_id_user)
I'd like to warn you that this query is not standard SQL, in fact it selects fields which are neither included in the GROUP BY
clause nor are the result of a group function. 我想警告您,该查询不是标准的SQL,实际上,它选择的字段既不包含在
GROUP BY
子句中,也不包含在组函数的结果中。
Lastly, I think that the above could be simplified like this: 最后,我认为可以将以上内容简化如下:
SELECT idu
, fname
, lname
, id_file
, friendly_name
, file_name
, uploaded_by
, date_uploaded
, file_last_modified
, owner_id
, CASE owned_by
WHEN 'church' THEN church_name
WHEN 'user' THEN CONCAT(fname, ' ', lname)
ELSE NULL
END AS e_owner_name
, CASE owned_by
WHEN 'church' THEN id_church
WHEN 'user' THEN idu
END AS e_owner_id
FROM files
, file_affiliations
, churches
, users
GROUP BY file_id
HAVING owner_id = e_owner_id
didnt try it but something like that should work: 没有尝试过,但是类似的东西应该起作用:
SELECT idu,fname,lname,id_file,friendly_name,file_name,uploaded_by,date_uploaded,
file_last_modified,owner_id,
CASE WHEN owned_by='church' THEN church_name WHEN owned_by='user' THEN CONCAT(fname, ' ', lname) END AS e_owner_name,
CASE WHEN owned_by='church' THEN id_church END AS e_owner_id_church,
CASE WHEN owned_by='user' THEN idu END AS e_owner_id_user
FROM files,file_affiliations,churches,users
GROUP BY file_id
HAVING owner_id = COALESCE(e_owner_id_church, e_owner_id_church, e_owner_id_user)
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