hive sql 的not exist

NOT EXISTS是一种用于在查询中检查另一个查询是否返回任何行的条件运算符。如果另一个查询返回任何行，则NOT EXISTS返回false，否则返回true。

语法：

SELECT column1, column2, ...
FROM table1
WHERE NOT EXISTS (SELECT column1 FROM table2 WHERE condition);

例子：

假设我们有两个表：`orders`和`customers`。我们想找出没有任何订单的客户。我们可以使用以下查询：

SELECT *
FROM customers
WHERE NOT EXISTS (SELECT * FROM orders WHERE orders.customer_id = customers.customer_id);

这个查询将返回一个包含没有订单的所有客户的结果集。如果存在订单，则子查询将返回一行或多行，然后NOT EXISTS将返回false，因此这些行将被排除在结果集之外。

相关问题

`path` does not exist:

`path` does not exist指的是指定的路径不存在。这个错误可能在不同的环境和情况下出现。对于Hive执行过程中遇到input path does not exists的错误，原因是Hive的元数据库中存储了HDFS上没有的分区目录，可能是因为误删除了外表数据导致的。而对于在使用vscode运行监控ts文件自动编译生成js时报错无法启动的问题，错误信息显示"error TS5058: The specified path does not exist"，解决方案是检查指定的路径是否正确并存在。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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[root@zhaosai conf]# sqoop import --connect jdbc:mysql://zhaosai:3306/mydb --username root --password jqe6b6 --table news --target-dir /user/news --fields-terminated-by “;” --hive-import --hive-table news -m 1 Warning: /opt/programs/sqoop-1.4.7.bin__hadoop-2.6.0/../hbase does not exist! HBase imports will fail. Please set $HBASE_HOME to the root of your HBase installation. Warning: /opt/programs/sqoop-1.4.7.bin__hadoop-2.6.0/../hcatalog does not exist! HCatalog jobs will fail. Please set $HCAT_HOME to the root of your HCatalog installation. Warning: /opt/programs/sqoop-1.4.7.bin__hadoop-2.6.0/../accumulo does not exist! Accumulo imports will fail. Please set $ACCUMULO_HOME to the root of your Accumulo installation. Warning: /opt/programs/sqoop-1.4.7.bin__hadoop-2.6.0/../zookeeper does not exist! Accumulo imports will fail. Please set $ZOOKEEPER_HOME to the root of your Zookeeper installation. 23/06/10 16:07:14 INFO sqoop.Sqoop: Running Sqoop version: 1.4.7 23/06/10 16:07:15 WARN tool.BaseSqoopTool: Setting your password on the command-line is insecure. Consider using -P instead. 23/06/10 16:07:15 INFO manager.MySQLManager: Preparing to use a MySQL streaming resultset. 23/06/10 16:07:15 INFO tool.CodeGenTool: Beginning code generation 23/06/10 16:07:15 ERROR sqoop.Sqoop: Got exception running Sqoop: java.lang.RuntimeException: Could not load db driver class: com.mysql.jdbc.Driver java.lang.RuntimeException: Could not load db driver class: com.mysql.jdbc.Driver at org.apache.sqoop.manager.SqlManager.makeConnection(SqlManager.java:875) at org.apache.sqoop.manager.GenericJdbcManager.getConnection(GenericJdbcManager.java:59) at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:763) at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:786) at org.apache.sqoop.manager.SqlManager.getColumnInfoForRawQuery(SqlManager.java:289) at org.apache.sqoop.manager.SqlManager.getColumnTypesForRawQuery(SqlManager.java:260) at org.apache.sqoop.manager.SqlManager.getColumnTypes(SqlManager.java:246) at org.apache.sqoop.manager.ConnManager.getColumnTypes(ConnManager.java:327) at org.apache.sqoop.orm.ClassWriter.getColumnTypes(ClassWriter.java:1872) at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1671) at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:106) at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:501) at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:628) at org.apache.sqoop.Sqoop.run(Sqoop.java:147) at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70) at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:183) at org.apache.sqoop.Sqoop.runTool(Sqoop.java:234) at org.apache.sqoop.Sqoop.runTool(Sqoop.java:243) at org.apache.sqoop.Sqoop.main(Sqoop.java:252)

这段代码是使用 Sqoop 工具将 MySQL 数据库中的 news 表导入到 Hadoop 的 HDFS 中，并且使用 Hive 表示，并且在导入过程中使用了分隔符“;”。但是在执行过程中出现了一个异常，提示无法加载数据库驱动类 com.mysql.jdbc.Driver。可能是因为没有将 mysql-connector-java.jar 包添加到 Sqoop 的 classpath 中导致的。需要将该 jar 包添加到 Sqoop 的 lib 目录下，并重新执行该命令。