使用UPDATE，SET，WHERE和LIKE的Sqlite语句未更新所有记录

Question

I am using the 'Execute SQL' feature in sql gui tool 'SQLite Database Browser 2.0 b1.'

I am not sure if the problem I am facing is because of a bug within the Browser or if my SQL is just wrong. I do know that I have found several bugs within the Browser tool.

Anyhow. Here is the problem I am dealing with currently...

I have two tables in a database:

TOYS
------------------------------
TOY_ID   TOY_DESC
------------------------------
1         Green truck, plastic
2         Doll, plastic, wood
3         Stuffed cloth animal
4         Board game cardboard and plastic
etc .....

MATERIALS
-----------------------------
TOY_ID     PLASTIC
-----------------------------
1
2
3
4
etc ......

I am trying to update the MATERIALS table so that IF the TOY_DESC that corresponds with the matching TOY_ID in the TOYS table, contains the word 'plastic', that it should insert the number 1 into the PLASTIC column in the MATERIALS table. This is what I have tried:

UPDATE MATERIALS SET PLASTIC = 1 WHERE TOY_ID = (SELECT TOY_ID FROM TOYS WHERE TOY_DESC LIKE '%plastic%');

when I tried this it did nothing.

then I tried...

UPDATE MATERIALS SET PLASTIC = 1 WHERE TOY_ID = (SELECT TOY_ID FROM TOYS WHERE TOY_DESC LIKE "%plastic%");

which then gave me:

MATERIALS
-----------------------------
TOY_ID     PLASTIC
-----------------------------
 1          1
 2
 3
 4
 etc ......

then I tried...

UPDATE MATERIALS SET PLASTIC = 1 WHERE TOY_ID = (SELECT TOY_ID FROM TOYS WHERE TOY_DESC LIKE '%plastic,%');

and that updated only one more record:

MATERIALS
-----------------------------
TOY_ID     PLASTIC
-----------------------------
1            1
2            1
3
4
etc ......

But still, it didn't update ALL of the records that contained the word plastic in the description!! I don't get it. why aren't all the records updating? I could understand if there was some other type of symbol or character on the end of the words, but there isn't. it's like exactly the same word in the other descriptions and they are ALL being skipped! I am further confused as to why the update didn't work at ALL until I replaced the single quotations with double quotations. Is this because of a difference in database type (sqlite vs. mysql)?

EDIT**:

I tried the suggestion from the poster below to break it down further to see where the problem might be. When I just do:

SELECT TOY_ID FROM TOYS WHERE TOY_DESC LIKE '%plastic%'

I successfully get a list of all the records that contain the word plastic in the description. So the LIKE statement isn't the problem. The question now is how do I get this to be reflected in the MATERIALS table?

I'm guessing I somehow need a loop for each match?

Answer 1

Troubleshoot your query by breaking down the components of it. Run nested/sub queries first:

SELECT TOY_ID FROM TOYS WHERE TOY_DESC LIKE "%plastic%"

Does it give you the results you expect?

Now you can focus on the like expression. I am no sqllite expert, but it looks as though %like% would require characters on both sides. So you could do:

SELECT TOY_ID FROM TOYS 
WHERE 
     TOY_DESC LIKE "%plastic%" 
  OR TOY_DESC LIKE "plastic%" 
  OR TOY_DESC LIKE "%plastic"

There are some other possibilities here: SQLite query, 'LIKE'

UPDATE: Great, now you know you are getting the expected IDs and don't have to mess with that subquery anymore. Now try instead of WHERE TOY_ID = ( use WHERE TOY_ID in (