如何使用动态SQL声明从表名派生的列名？ [英] How do I use dynamic SQL to declare a column name derived from a table name?

问题描述

基于 Tony的答案在这个问题：

如果我想做这样的事情，

If I want to do something like this,

CREATE PROCEDURE A(tab IN VARCHAR2) IS
tab.col_name <column> --static declaration (column name always remains the same)
BEGIN
   EXECUTE IMMEDIATE 'INSERT INTO ' || tab(col_name) || 'VALUES(123)';
END A;

在上述情况下如何使用动态SQL？

推荐答案

此示例传入一个表名和一个列名：

This example passes in a table name and a column name:

CREATE PROCEDURE A
  ( tab IN VARCHAR2
  , col_name IN VARCHAR2
  ) IS
BEGIN
   EXECUTE IMMEDIATE 'INSERT INTO ' || tab || '(' || col_name || ') VALUES(123)';
END A;

您需要认识到EXECUTE IMMEDIATE之后的所有内容都必须是包含某些有效SQL的字符串。验证它的一个好方法是将其设置为变量并将其打印到屏幕上：

You need to realise that everything after EXECUTE IMMEDIATE must be a string that contains some valid SQL. A good way to verify this is to set it up in a variable and print it to the screen:

CREATE PROCEDURE A
  ( tab IN VARCHAR2
  , col_name IN VARCHAR2
  ) IS
   v_sql VARCHAR2(2000);
BEGIN
   v_sql := 'INSERT INTO ' || tab || '(' || col_name || ') VALUES(123)';
   DBMS_OUTPUT.PUT_LINE('SQL='||v_sql);
   EXECUTE IMMEDIATE v_sql;
END A;

然后应在SQL Plus中显示类似以下内容：

This should then display something like the following in SQL Plus:

SQL = INSERT INTO mytable（mycolumn）
VALUES（123）

SQL=INSERT INTO mytable(mycolumn) VALUES(123)

（提供的服务器输出已打开）。

(provided server output is turned on).

编辑：由于您希望列名是始终具有相同的值，可以这样操作：

EDIT: Since you want the column name to be a local variable that always has the same value, this could be done as:

CREATE PROCEDURE A (tab IN VARCHAR2)
IS
   col_name VARCHAR2(30) := 'MYCOLUMN';
   v_sql VARCHAR2(2000);
BEGIN
   v_sql := 'INSERT INTO ' || tab || '(' || col_name || ') VALUES(123)';
   DBMS_OUTPUT.PUT_LINE('SQL='||v_sql);
   EXECUTE IMMEDIATE v_sql;
END A;

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