Question

在使用SQL Server Management Studio的SQL编码中，我可以从插入或删除时具有不同行数的表中删除。我更新表A之后，如果表B中有表项，我想删除表A中的匹配项。我的想法是最后只有表A中已更新的行。我有10列，但将使用4到把事情简单化。

CREATE TRIGGER utr_Updates
ON  tableA
AFTER UPDATE
AS BEGIN
    SET NOCOUNT ON;
    EXEC usp_updates
END

CREATE PROCEDURE usp_Updates
AS
BEGIN
    IF EXISTS (SELECT * FROM tableA 
               WHERE col1 IN (SELECT DISTINCT col1 FROM tableB))
        DELETE FROM tableA 
        WHERE col1 IN (SELECT DISTINCT col1 FROM tableB)

    IF EXISTS (SELECT * FROM tableA 
               WHERE col2 IN (SELECT DISTINCT col2 FROM tableB))
        DELETE FROM tableA 
        WHERE col2 IN (SELECT DISTINCT col2 FROM tableB)

    IF EXISTS (SELECT * FROM tableA 
               WHERE col3 IN (SELECT DISTINCT col3 FROM tableB))
        DELETE FROM tableA 
        WHERE col3 IN (SELECT DISTINCT col3 FROM tableB)

    IF EXISTS (SELECT * FROM tableA 
               WHERE col4 IN (SELECT DISTINCT col4 FROM tableB))
        DELETE FROM tableA 
        WHERE col4 IN (SELECT DISTINCT col4 FROM tableB)
END

START POINT

                  START

    TABLE A                TABLE B
col1 W, X, Y, Z         col1 W, X, Y, Z
col2 1, 2, 3, 4         col2 1, 2, 3, 4
col3 A, 5, 6, D         col3 A, 5, 6, D
col4 7, B, C, D         col3 7, B, C, D

表A更新了col1和col3

               AFTER UPDATE

    TABLE A                TABLE B
col1 W, S, Y, Z         col1 W, X, Y, Z
col2 1, 2, 3, 4         col2 1, 2, 3, 4
col3 A, 5, 1, D         col3 A, 5, 6, D
col4 7, B, C, D         col3 7, B, C, D

期望的结果

     TABLE A   
 col1 W, S, Y, Z
 col3 A, 5, 1, D

Answer 1

您可以使用... streamState = waitOnStreamForState(stream, 4); int i = stream.readInt(); ... private static int waitOnStreamForState(DataInputStream stream, int nBytes) throws IOException { return waitOnStream(stream, nBytes, STREAM_ACTIVITY_THRESHOLD, STREAM_POLL_INTERVAL) ? STREAM_STATE_ACTIVE : STREAM_STATE_INACTIVE; private static boolean waitOnStream(DataInputStream stream, int nBytes, long timeout, long pollInterval) throws IOException { int timeWaitingForAvailable = 0; while( stream.available() < nBytes ){ if( timeWaitingForAvailable >= timeout && timeout > 0 ){ return false; } try{ Thread.sleep(pollInterval); }catch( InterruptedException e ){ Thread.currentThread().interrupt(); return (stream.available() >= nBytes); } timeWaitingForAvailable += pollInterval; } return true; }：

NOT EXISTS

或者，在SQL Server中，您可以使用select a.* from a where not exists (select 1 from b where b.col1 = a.col1 and b.col2 = a.col2 and b.col3 = a.col3 and b.col4 = a.col4 );：

EXCEPT

如何使用SQL删除两个单独表中匹配的行？

1 个答案: