java - 在java中使用mysql变量(用于排名查询)

Question

我想在 MySQL 表中为用户创建一个排名，按他们的分数排序。我已经找到了一个很好的查询，但是这个查询仅适用于 phpmyadmin，不适用于 java...

我得到了以下 MySQL 查询，它可以在 phpmyadmin 中很好地创建排名:

SET @r=0; UPDATE `hg_stats` SET `stats_rank`= @r:= (@r+1) ORDER BY `stats_score` DESC;

在 Java 中:

try {
            preparedStatement = connection.prepareStatement("SET @r=0; UPDATE `hg_stats` SET `stats_rank`= @r:= (@r+1) ORDER BY `stats_score` DESC;");
            preparedStatement.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace();
        }

我收到以下错误并且查询不起作用:

[00:09:50] [Server thread/WARN]: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UPDATE `hg_stats` SET `stats_rank`= @r:= (@r+1) ORDER BY `stats_score` DESC' at line 1
[00:09:50] [Server thread/WARN]:    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[00:09:50] [Server thread/WARN]:    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
[00:09:50] [Server thread/WARN]:    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
[00:09:50] [Server thread/WARN]:    at java.lang.reflect.Constructor.newInstance(Unknown Source)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.Util.getInstance(Util.java:382)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1052)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3593)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3525)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1986)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2140)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2626)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2111)
[00:09:50] [Server thread/WARN]:    at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2273)
[00:09:50] [Server thread/WARN]:    at com.jolbox.bonecp.PreparedStatementHandle.executeQuery(PreparedStatementHandle.java:174)
[00:09:50] [Server thread/WARN]:    at de.hg_pvp.game.stats.StatsManager.executeQuery(StatsManager.java:340)
[00:09:50] [Server thread/WARN]:    at de.hg_pvp.game.stats.StatsManager.win(StatsManager.java:292)
[00:09:50] [Server thread/WARN]:    at de.hg_pvp.game.HungerGamesPlugin.onDisable(HungerGamesPlugin.java:149)
[00:09:50] [Server thread/WARN]:    at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:252)
[00:09:50] [Server thread/WARN]:    at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:348)
[00:09:50] [Server thread/WARN]:    at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:424)
[00:09:50] [Server thread/WARN]:    at org.bukkit.plugin.SimplePluginManager.disablePlugins(SimplePluginManager.java:417)
[00:09:50] [Server thread/WARN]:    at org.bukkit.craftbukkit.v1_7_R2.CraftServer.disablePlugins(CraftServer.java:398)
[00:09:50] [Server thread/WARN]:    at net.minecraft.server.v1_7_R2.MinecraftServer.stop(MinecraftServer.java:384)
[00:09:50] [Server thread/WARN]:    at net.minecraft.server.v1_7_R2.MinecraftServer.run(MinecraftServer.java:507)
[00:09:50] [Server thread/WARN]:    at net.minecraft.server.v1_7_R2.ThreadServerApplication.run(SourceFile:618)

Answer 1

您所说的查询实际上是一系列查询，以分号分隔。

但是您不能通过 JDBC 一次运行多个查询。

你需要这样的东西:

PreparedStatement ps1 = connection.prepareStatement
      ("SET @r=0");
ps1.ExecuteQuery();

PreparedStatement ps2 = connection.prepareStatement
      ("UPDATE `hg_stats` SET `stats_rank`= @r:= (@r+1) ORDER BY `stats_score` DESC");
ps2.ExecuteQuery();