Why Am I Getting an \'Undeclared Variable\' Error in My SELECT INTO Query?

Error: "Undeclared Variable" in SELECT INTO Query

When executing a SELECT INTO query, users may encounter the error message "Undeclared variable" when specifying the target variable to store the selected data.

To address this error, it's important to understand that SELECT INTO queries create a temporary memory table with the selected data. This temporary table is stored in a variable with the same name as the specified target variable.

Unfortunately, when using SELECT INTO outside of stored procedures or functions, MySQL may not recognize the target variable as a declared variable. To resolve this issue, use the INSERT ... SELECT syntax instead.

INSERT INTO newsletter_to_send
SELECT id_subscriber
FROM subscribers 

For more information on INSERT ... SELECT queries, refer to the MySQL documentation:

http://dev.mysql.com/doc/refman/5.1/en/insert-select.html

Remember to review the WHERE clause if necessary to avoid selecting unnecessary data.

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