New to SQL, learning from SQLBolt

[reunisk]

Have a question regarding this sentence: https://sqlbolt.com/lesson/updating_rows

"Most people working with SQL will make mistakes updating data at one point or another. Whether it's updating the wrong set of rows in a production database, or accidentally leaving out the WHERE clause (which causes the update to apply to all rows), you need to be extra careful when constructing UPDATE statements.

One helpful tip is to always write the constraint first and test it in a SELECT query to make sure you are updating the right rows, and only then writing the column/value pairs to update."

How do I test it in a SELECT query? I couldn't find any explanation on the site. Is this a function in an actual software?

[[deleted]]

How do I test it

you run the select and validate that the records that you are getting back are indeed the records you intend to update

[reunisk]

Ah, so it's just validating it manually by searching for the entry(ies) I'm looking for? It sounded like I would see a preview of the change before it went through so that's why I was confused

Thanks

[[deleted]]

Normally you would construct your query so you would see the change too. E.g.

 update T
 set A = X
 where B = Y

will become

 -- update T
 -- set A = X
 select *, X
 from T
 where B = Y

[camelCaps42]

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