在sql查询中动态查找表的列名 [英] Dynamically look up column names for a table while in an sql query

问题描述

我正在写SQL(用于Oracle)，

I'm writing SQL (for Oracle) like:

INSERT INTO Schema1.tableA SELECT * FROM Schema2.tableA;

其中Schema1.tableA和Schema2.tableA具有相同的列.但是，这似乎是不安全的，因为在SELECT中返回的列的顺序是不确定的.我应该做的是:

where Schema1.tableA and Schema2.tableA have the same columns. However, it seems like this is unsafe, since the order of the columns coming back in the SELECT is undefined. What I should be doing is:

INSERT INTO Schema1.tableA (col1, col2, ... colN) 
SELECT (col1, col2, ... colN) FROM Schema2.tableA;

我正在使用一些脚本对很多表进行此操作，所以我想做的是编写如下内容:

I'm doing this for lots of tables using some scripts, so what I'd like to do is write something like:

INSERT INTO Schema1.tableA (foo(Schema1.tableA)) 
SELECT (foo(Schema1.tableA)) FROM Schema2.tableA;

其中foo是一些漂亮的魔术，它可以从表1中提取列名并以适当的语法打包它们.有想法吗?

Where foo is some nifty magic that extracts the column names from table one and packages them in the appropriate syntax. Thoughts?

推荐答案

此PL/SQL应该这样做:

This PL/SQL should do it:

declare
    l_cols long;
    l_sql  long;
begin
    for r in (select column_name from all_tab_columns
              where  table_name = 'TABLEA'
              and    owner = 'SCHEMA1'
             )
    loop
       l_cols := l_cols || ',' || r.column_name;
    end loop;

    -- Remove leading comma
    l_cols := substr(l_cols, 2);

    l_sql := 'insert into schema1.tableA (' || l_cols || ') select ' 
             || l_cols || ' from schema2.tableA';

    execute immediate l_sql;

end;
/

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