Question

我有这个mysql查询：

SELECT Files.GUID, Files.Name, Files.Type, Files.Visibility, Files.CreationDate, Files.OwnerUser, Date, BackupsCount
FROM Files
  LEFT JOIN (
    SELECT FileGUID, Date, COUNT(*) AS BackupsCount
    FROM Versions
    GROUP BY FileGUID
  ) Versions ON Files.GUID = Versions.FileGUID
WHERE Files.ParentFolder = '96251A8B-B2A8-416B-92D7-3509E6A645C7'
ORDER BY Files.Type DESC, CreationDate ASC
LIMIT 0, 50

我想知道这个查询会返回多少记录如果LIMIT指令不存在，我用Google搜索并发现我需要添加SELECT SQL_CALC_FOUND_ROWS和{{ 1}}

我的问题是：我无法让它发挥作用：

SELECT FOUND_ROWS();

假设这是个好主意（我的意思是执行一个查询而不是两个单独的查询），如何让SELECT SQL_CALC_FOUND_ROWS * FROM ( SELECT Files.GUID, Files.Name, Files.Type, Files.Visibility, Files.CreationDate, Files.OwnerUser, Date, BackupsCount FROM Files LEFT JOIN ( SELECT FileGUID, Date, COUNT(*) AS BackupsCount FROM Versions GROUP BY FileGUID ) Versions ON Files.GUID = Versions.FileGUID WHERE Files.ParentFolder = '96251A8B-B2A8-416B-92D7-3509E6A645C7' ORDER BY Files.Type DESC, CreationDate ASC LIMIT 0, 50) -- Find total rows SELECT FOUND_ROWS()使用此查询？

Answer 1

查询应该是这样的：

SELECT SQL_CALC_FOUND_ROWS Files.GUID, Files.Name, Files.Type, Files.Visibility, Files.CreationDate, Files.OwnerUser, Date, BackupsCount
FROM Files
  LEFT JOIN (
    SELECT FileGUID, Date, COUNT(*) AS BackupsCount
    FROM Versions
    GROUP BY FileGUID
  ) Versions ON Files.GUID = Versions.FileGUID
WHERE Files.ParentFolder = '96251A8B-B2A8-416B-92D7-3509E6A645C7'
ORDER BY Files.Type DESC, CreationDate ASC
LIMIT 0, 50

Answer 2

这个想法是正确的，第二个查询几乎是即时的。但是你必须在SELECT之后添加关键字，不再是：

SELECT Files.GUID, Files.Name, Files.Type, ...

变为

SELECT SQL_CALC_FOUND_ROWS Files.GUID, Files.Name, Files.Type, ...

然后会填充找到的行数，您就可以恢复它了。

如果您想运行一个检索查询，但是您能够执行多个查询，那么您可以执行此操作（这是两个查询）：

SELECT COUNT(*) INTO @FOUNDROWS FROM ( YOUR_QUERY_WITHOUT_SELECT ) AS orig;

并通过将@FOUNDROWS as foundrows添加到字段来更改您的检索查询：

SELECT ...YOUR FIELDS..., @FOUNDROWS AS foundrows FROM...

最后，您可以将JOIN作为包含两个查询的单个查询运行：

SELECT ALL_YOUR_FIELDS, counter.FOUND_ROW_NUMBER FROM
( YOUR_QUERY_WITH_LIMIT ) AS limited
JOIN ( SELECT COUNT(*) AS FOUND_ROW_NUMBER FROM YOUR_QUERY ) AS counter;

Answer 3

A very simple example


 "SELECT SUM(final_cost) as final_cost,
SUM(call_discount) as discount_cost,
(SELECT COUNT(*) FROM call_records WHERE transaction_type ='call' AND account_id='$account_id' AND time_of_call>='$from' AND time_of_call<='$to' ) as calls,
(SELECT COUNT(*) FROM call_records WHERE transaction_type ='text' AND account_id='$account_id' AND time_of_call>='$from' AND time_of_call<='$to' ) as texts,
(SELECT COUNT(*) FROM call_records WHERE transaction_type ='appointment' AND account_id='$account_id' AND time_of_call>='$from' AND time_of_call<='$to' ) as appts
 FROM
 call_records
 WHERE account_id='$account_id'
 AND time_of_call>='$from'
 AND time_of_call<='$to' "

从查询返回的总mysql结果具有限制：FOUND_ROWS错误

3 个答案: