Understanding the Purpose and Impact of WHERE 1=1 in SQL Queries

Have you ever seen a SELECT query with a WHERE 1=1 condition? This condition is equivalent to WHERE TRUE , meaning it returns the same result as a query without a WHERE clause. The query optimizer almost certainly removes it, so it does not affect execution time.

The question then becomes: what is the purpose of WHERE 1=1 ? The following sections answer this.

Does WHERE 1=1 improve query execution?

As mentioned, the optimizer removes the hard‑coded WHERE 1=1 clause, so we should not see any reduction in query execution time. To verify this, we ran a query in Navicat with and without the WHERE 1=1 clause.

First, the query on the Sakila sample database that retrieves customers who rented movies from the Lethbridge store:

The information tab shows a runtime of 0.004 seconds (highlighted in a red box).

Now we run the same query but add the WHERE 1=1 clause:

The runtime is again 0.004 seconds. Although execution times can vary slightly due to many factors, we can confidently say that the WHERE 1=1 clause has no impact.

So why use it? In short, it’s a convenience.

For convenience

In fact, the WHERE 1=1 clause is an idiom adopted by many developers to simplify the use of both static and dynamic SQL statements.

In static SQL

When adding conditions to a query that already contains WHERE 1=1 , every subsequent condition is prefixed with AND , making it easier to comment out experimental conditions.

This is similar to the trick of adding a comma before a column name rather than after it, which also makes commenting easier.

In dynamic SQL

It is also a common practice when building SQL queries programmatically. Starting with WHERE 1=1 allows developers to append additional conditions such as and customer.id=:custId depending on whether a customer ID is provided. This makes it easy to add the next condition prefixed with and ... . Below is a hypothetical example:

stmt  = "SELECT * "
stmt += "FROM TABLE "
stmt += "WHERE 1=1 "
if user chooses option a then stmt += "and A is not null "
if user chooses option b then stmt += "and B is not null "
if user chooses option c then stmt += "and C is not null "
if user chooses option d then stmt += "and D is not null "

Summary

In this article we learned the answer to the age‑old question “What is the purpose of WHERE 1=1 ?” It is not an advanced optimization technique; rather, it is a stylistic convention adopted by some developers to make query construction and modification easier.