SQL“同时"将表数据读取到变量 [英] SQL 'while' to read a table data to a variable

问题描述

如何编写while循环以将表中的数据填充到要在单独查询中使用的变量? 例如:select ITEM from Table1

How could I write a while loop to populate data from a table to a variable to be used in a seperate query ? EX: select ITEM from Table1

ITEM
A0001
B0001
C0003
D0005
E0032

如果我可以在列ITEM至@var1下获得所有结果，然后将其用于单独的查询中，例如:

If I can get all that results here under column ITEM to @var1 and then use it in a seperate query like:

select * 
from Table2 
where @var1 = Item_table2  <-- a random column in table2

此查询应将@var1从A0001到E0032匹配到Table2中的Item_table2列.

This query should match @var1 from A0001 to E0032 to the Item_table2 column in Table2.

推荐答案

所以这是您的第一个表格:

So here is your first table:

mysql> select * from item_table1;
+-------+
| item  |
+-------+
| A0001 |
| B0001 |
| C0003 |
| D0005 |
| E0032 |
+-------+
5 rows in set (0.01 sec)

现在，我们需要基于此表创建一个视图.视图是您在问题中通过@var1调用的等效概念:

Now, we need to create a view based on this table. The view is the equivalent concept you call in your question by @var1:

mysql> create view item_table2 as (select * from item_table1);
Query OK, 0 rows affected (0.30 sec)

让我们检查一下视图item_table2(用您自己的话说是@var1):

Let's check our view item_table2 (@var1 in your own words):

mysql> select * from item_table2;
+-------+
| item  |
+-------+
| A0001 |
| B0001 |
| C0003 |
| D0005 |
| E0032 |
+-------+
5 rows in set (0.00 sec)

现在，您可以像这样在item_table1中从item_table2中选择任何项:

Now, you can select any item from item_table2 that exists in your item_table1 like this:

 select it2.item from item_table2 it2 where it2.item='A0001'

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