SELECT INTO and Error: Undeclared Variable
When attempting to execute the query:
SELECT id_subscriber INTO newsletter_to_send FROM subscribers
You encounter an error:
#1327 - Undeclared variable: newsletter_to_send
Cause:
The error arises because the variable newsletter_to_send is not declared or initialized before its use in the query.
Solution:
To resolve this issue, you need to use the INSERT ... SELECT syntax instead of the SELECT INTO syntax. The correct query should be:
INSERT INTO newsletter_to_send SELECT id_subscriber FROM subscribers
The INSERT ... SELECT syntax allows you to insert multiple rows into a table by using the results of a subquery.
Additional Note:
It's worth considering if there is a need for a WHERE clause in the subquery to filter the results and potentially prevent inserting unwanted rows into the newsletter_to_send table.
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