Question

我有2张桌子：

`T1列-> a，b，c，x
T2 columns -> d, e, f

join就像这样：

    if(a != NULL and a != c) 
     join condition is (a = f and b = d)
    else if(a == NULL or a == c)
     join condition is (c = f and x = e)

如何在sql中执行此操作？

Answer 1

您的数据库设计很重要，但是为了回答您的问题，您可以只使用AND和OR：

SELECT *
FROM Table1 T1
JOIN Table2 T2 ON (T1.a IS NOT NULL AND T1.a <> T1.c AND T1.a = T2.F AND T1.b = T2.d)
               OR (COALESCE(T1.a,T1.c) = T1.c AND T1.c = T2.f AND T1.x = T2.e)

Answer 2

您可能可以摆脱工会的束缚。这样的事情可能会起作用。

SELECT *
FROM T1
       INNER JOIN T2 ON t1.a = t2.f AND t1.b = t2.d
WHERE T1.a != T1.c
  AND T1.a IS NOT NULL
UNION DISTINCT
SELECT *
FROM T1
       INNER JOIN T2 ON t1.c = t2.f AND t1.b = t2.e
WHERE T1.a IS NULL
   OR T1.a = T1.c

Answer 3

尝试使用12:17:44.040 [DEMO-4] DEBUG o.h.r.t.b.j.i.JdbcResourceLocalTransactionCoordinatorImpl - JDBC transaction marked for rollback-only (exception provided for stack trace) java.lang.Exception: exception just for purpose of providing stack trace at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.markRollbackOnly(JdbcResourceLocalTransactionCoordinatorImpl.java:265) [hibernate-core-5.0.6.Final.jar:5.0.6.Final] at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.beforeCompletionCallback(JdbcResourceLocalTransactionCoordinatorImpl.java:156) [hibernate-core-5.0.6.Final.jar:5.0.6.Final] at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl.access$100(JdbcResourceLocalTransactionCoordinatorImpl.java:38) [hibernate-core-5.0.6.Final.jar:5.0.6.Final] at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.commit(JdbcResourceLocalTransactionCoordinatorImpl.java:231) [hibernate-core-5.0.6.Final.jar:5.0.6.Final] at org.hibernate.engine.transaction.internal.TransactionImpl.commit(TransactionImpl.java:65) [hibernate-core-5.0.6.Final.jar:5.0.6.Final] at org.springframework.orm.hibernate5.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:581) [spring-orm-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761) [spring-tx-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730) [spring-tx-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:485) [spring-tx-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:291) [spring-tx-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) [spring-tx-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.aop.interceptor.AsyncExecutionInterceptor$1.call(AsyncExecutionInterceptor.java:108) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE] at org.springframework.aop.interceptor.AsyncExecutionAspectSupport$CompletableFutureDelegate$1.get(AsyncExecutionAspectSupport.java:237) [spring-aop-4.2.4.RELEASE.jar:4.2.4.RELEASE] at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1590) [na:1.8.0_171] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_171] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_171] at java.lang.Thread.run(Thread.java:748) [na:1.8.0_171] 12:17:44.043 [DEMO-4] DEBUG o.s.o.h.HibernateTransactionManager - Initiating transaction rollback after commit exception org.hibernate.AssertionFailure: null id in com.app.model.FieldValue entry (don't flush the Session after an exception occurs)。

CASE

在if-else条件下加入

3 个答案: