我需要通过传递表名来更改一个与netezza中的其他表数据类型相同的表数据类型？

Question

我有一个名为L0的表，它创建为：

create table L0 (
   name varchar,
   number varchar,
   address varchar
);

L0中显示的所有列的数据类型为varchar，

我有另一个表L1，它创建为：

create table L1 (
   name varchar,
   number int,
   address char
);

我想通过传递表名将L0表的数据类型转换为与L1表相同。

我希望最终查询看起来像这样：

select cast(name as varchar), cast(number as int), cast(address as char) from L0
minus
select * from L1:

这样做的方法是什么？

Answer 1

如果你在Netezza中安装了group_concat UDA，那么你可以使用columns元数据视图获得所需的输出

create table L0 (
   name varchar(20),
   number varchar(10),
   address varchar(50)
);

create table L1 (
   name varchar(50),
   number int,
   address char(20)
);

查询：

SELECT 'select ' || system..group_concat('cast (' || a.column_name || ' as ' || b.data_type || ')') || ' from ' || a.table_name || ' minus select ' || system..group_concat(b.column_name) || ' from ' || b.table_name || ' ;'
FROM columns a
    ,columns b
WHERE a.column_name = b.column_name
    AND a.table_name = 'L0'
    AND b.table_name = 'L1'
    AND a.table_catalog = 'TEST' --- this is the current database name 
GROUP BY a.table_name
    ,b.table_name;

<强>输出：

    SELECT cast(ADDRESS AS CHARACTER(20))
    ,cast(NAME AS CHARACTER VARYING(50))
    ,cast(NUMBER AS INTEGER)
FROM L0 minus

SELECT ADDRESS
    ,NAME
    ,NUMBER
FROM L1;

修改 使用存储过程

的替代方法

CREATE OR REPLACE PROCEDURE GRP_CONCAT(varchar(50),varchar(50))
RETURNS VARCHAR(ANY)
EXECUTE AS OWNER
LANGUAGE NZPLSQL AS
BEGIN_PROC
DECLARE
    TABLE_NAME1 ALIAS FOR $1;
    TABLE_NAME2 ALIAS for $2;
    return_text varchar(10000) := 'SELECT';
    x record;
BEGIN
FOR x IN    select a.column_name as colname,b.data_type datatype
FROM columns a
    ,columns b
WHERE a.column_name = b.column_name
    AND a.table_name = TABLE_NAME1
    AND b.table_name = TABLE_NAME2
    order by b.ordinal_position
    LOOP
    return_text := return_text || ' CAST ('||x.colname ||' as '||x.datatype||') , ';

    end loop;



     return_text := trim(return_text,' , ')||' FROM '||TABLE_NAME1 || ' minus select * from  '||TABLE_NAME2||';';

     return return_text;
EXCEPTION WHEN OTHERS THEN
RAISE NOTICE 'ERROR: %', SQLERRM;
RETURN 1;
END;

END_PROC;

输出

致电GRP_CONCAT（＆＃39; L0＆＃39;，＆＃39; L1＆＃39;）;

SELECT CAST(NAME AS CHARACTER VARYING(50))
    ,CAST(NUMBER AS INTEGER)
    ,CAST(ADDRESS AS CHARACTER(20))
FROM L0 minus

SELECT *
FROM L1;