Why Use `WHERE 1=1 AND ` in SQL Queries?

Deep dive into SQL statementsWHERE 1=1 AND

In the world of SQL, the use of the WHERE clause is very common. However, one particular structure WHERE 1=1 AND <条件> has attracted attention, and questions have been raised about its purpose and effectiveness.

SQL injection protection?

Some people think that this structure is used for SQL injection protection. However, its intended functionality is questionable. As mentioned before, the statement WHERE 1=1 AND 注入 OR 1=1 has the same result as 注入 OR 1=1, making the WHERE 1=1 clause invalid.

Convenience in implementation

A more reasonable explanation lies in the convenience of implementation. When building a SQL query, the condition may not be known at compile time, and the WHERE 1=1 prefix eliminates the need to determine whether the condition exists. Conditions can be connected using the AND operator, and the initial 1=1 provides a base for the AND chain.

It should be noted that the SQL engine will ignore the 1=1 condition to ensure minimal performance impact. Therefore, using WHERE 1=1 AND <条件> is primarily a programming convenience rather than a security measure.

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