Question

我有两个表，用户和会话。每个用户可以有多个会话。我想获取用户名和他最近一次会话的日期。但我需要这样做，以便能够返回按上次会话日期排序的数组。此外，某些用户可能没有会话，因此左连接将不返回任何日期。

SELECT u.name, max(s.sdate) FROM users u
LEFT JOIN sessions s ON s.uid=u.id
ORDER BY s.sdate
LIMIT 25,25

显然这不起作用，但我想要一些简单的东西。相似的东西？请注意，我还需要指定由于分页而返回的行集。这将是第2页。我确实看到了类似的帖子，但它们对我的使用来说过于复杂。

我保持这种简化以便于理解。

Answer 1

我相信你的情况你只需要按用户分组你的结果。尝试

  Preparing

Analyzing dependencies

Inspecting targets to integrate
  Using `ARCHS` setting to build architectures of target `Pods`: (``)

Finding Podfile changes
  - AFNetworking
  - Masonry
  - NIMSDK

Resolving dependencies of `Podfile`

Comparing resolved specification to the sandbox manifest
  - AFNetworking
  - Masonry
  - NIMSDK

Downloading dependencies

-> Using AFNetworking (2.5.4)

-> Using Masonry (0.6.2)

-> Using NIMSDK (1.2.0)
  - Running pre install hooks

Generating Pods project
  - Creating Pods project
  - Adding source files to Pods project
  - Adding frameworks to Pods project
  - Adding libraries to Pods project
  - Adding resources to Pods project
  - Linking headers
  - Installing targets
    - Installing target `AFNetworking` iOS 7.0
    - Installing target `Masonry` iOS 7.0
    - Installing target `Pods` iOS 7.0
  - Running post install hooks
  - Writing Xcode project file to `Pods/Pods.xcodeproj`
  - Writing Lockfile in `Podfile.lock`
  - Writing Manifest in `Pods/Manifest.lock`

Integrating client project

Integrating target `Pods` (`XXXX.xcodeproj` project)
  - Running post install hooks
    - cocoapods-stats from `/Library/Ruby/Gems/2.0.0/gems/cocoapods-stats-0.5.3/lib/cocoapods_plugin.rb`

Sending stats
      - AFNetworking, 2.5.4
      - Masonry, 0.6.2
      - NIMSDK, 1.2.0
      Failed to send stats:  SSL_connect returned=1 errno=0 state=SSLv2/v3 read server hello A: sslv3 alert handshake failure

通过左连接日期的Mysql顺序

1 个答案: