将表ID从一列复制到另一列，其中列数据在表之间匹配

Question

I have two tables, Fruits and Meals, and one of the columns in Meals is a varchar(100) with the fruits in them. I am changing this so that the column is instead the id of the fruit from the Fruits table, and I would like to set this by comparing the two tables and grabbing the id from the fruits table where the fruit columns match.

Table: Fruits   
id | fruit
1    apple
2    banana
3    orange

Table: Meals
id | Meal | Fruit
1    xxxx   apple
2    xxxx   apple
3    xxxx   orange
4    xxxx   banana
5    xxxx   orange
6    xxxx   orange
7    xxxx   apple

I've tried the following script, but I get the following error.

Update product_attribute set control_caption =
(
    Select DISTINCT T1.control_caption_id from control_caption T1
    INNER Join product_attribute T2
    On T1.control_caption = T2.control_caption
    Where T1.control_caption = T2.control_caption
)

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Answer 1

Depends on your RDBMS, but this should work for SQL Server:

Update pa
set pa.control_caption = cc.control_caption_id 
From product_attribute pa
   Join control_caption cc On 
         cc.control_caption = pa.control_caption

Answer 2

The Update Query can be simplified and a Join may be used instead of a subquery running the select statement.

Update P
    Set P.Control_Caption = C.Control_Caption_ID
    From Product_Attribute P
    join Control_Caption C on C.Control_Caption= P.Control_Caption

This runs on both SQL Server & Oracle.