Question

有人知道为什么这个查询语句在此查询中运行的很好吗，但是当我在同一个选择语句前添加cte时，会出现此错误：

SQL错误：ORA-00957：列名重复）

CREATE TABLE t1 AS 
SELECT * 
 FROM NS_F3 
 LEFT JOIN NS_FA2 
 ON NS_F3.PI_CANDIDATE_NUM = NS_FA2.PI_CANDIDATE_NUM 
 WHERE REGEXP_LIKE(NS_F3.TITLE, 'intern($|ship|[^a-z])', 'i');

Answer 1

这是因为表public void Send_Command(View v) { testClass(); Toast.makeText(getApplicationContext(), "Comando Enviado!", Toast.LENGTH_LONG).show(); } public static void testClass() { Thread cThread = new Thread(new ClientThread()); cThread.start(); } public static class ClientThread implements Runnable { String results = ""; public void run() { try { InetAddress serverAddr = InetAddress.getByName(serverIpAddress); System.out.println("C: Connecting..."); while (true) { results = ""; try { Socket socket = new Socket("192.168.1.77", 8888); BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream())); BufferedWriter out = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())); out.write("Test"); out.flush(); String inMsg = ""; boolean b = false; while (!b) { inMsg = in .readLine(); if (inMsg != "") b = true; } socket.close(); System.out.println("C: Closed."); } catch (Exception e) { System.out.println("S: Error" + e.toString()); } } } catch (Exception e) { System.out.println("C: Error" + e); } } }和NS_F3包含具有相同名称的列-在这种情况下，应使用列别名以避免重复的列名。

这里是一个例子：我正在创建一个简单表，作为斯科特NS_FA2表中几列的摘录：

EMP

将其加入SQL> create table t_first as select deptno, empno, ename from emp where rownum < 5; Table created.表：

DEPT

只要它可以在SQL> select * from t_first e join dept d on e.deptno = d.deptno; DEPTNO EMPNO ENAME DEPTNO DNAME LOC ---------- ---------- ---------- ---------- -------------- ------------- 20 7369 SMITH 20 RESEARCH DALLAS 20 7566 JONES 20 RESEARCH DALLAS 30 7521 WARD 30 SALES CHICAGO 30 7499 ALLEN 30 SALES CHICAGO ^^^^^^^^^ ^^^^^^^^ this is DEPTNO column ... ... and here's another one中使用，就不能在SELECT中使用：

CREATE TABLE

解决方案是使用列别名，例如：

SQL> create table test as
  2  select * from t_first e join dept d on e.deptno = d.deptno;
select * from t_first e join dept d on e.deptno = d.deptno
       *
ERROR at line 2:
ORA-00957: duplicate column name

为什么创建表显示ORA-00957：重复的列名

1 个答案: