How do I use dynamic SQL to declare a column name

问题:

Building on Tony's answer on this question:

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;

How can I use Dynamic SQL in the above case?

回答1:

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;

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;

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

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

(provided server output is turned on).

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;