How to Resolve 'user_id' Ambiguity in MySQL WHERE Clause?

MySQL: Resolving 'user_id' Ambiguity in WHERE Clause

When querying data from multiple tables using a JOIN operation, it's crucial to ensure that there is no ambiguity regarding which table a column reference belongs to. This issue arises when columns with identical names exist in the joined tables, as illustrated in the code below:

SELECT user.*, user_info.*
FROM user
INNER JOIN user_info ON user.user_id = user_info.user_id
WHERE user_id=1

The error message "user_id in where clause is ambiguous" indicates that the database cannot determine which table's user_id column is referenced in the WHERE clause. To resolve this ambiguity, it is necessary to specify the full table name along with the column name.

For instance, to filter the results based on the user_id column from the user table, the code should be modified as follows:

SELECT user.*, user_info.*
FROM user
INNER JOIN user_info ON user.user_id = user_info.user_id
WHERE user.user_id=1

By explicitly stating "user.user_id," the ambiguity is removed, and the database now knows that the WHERE clause is referring to the user_id column from the user table. This modification ensures that the query returns the intended results without any ambiguity.

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