What Is the Purpose of Using Where 1=1 in SQL Statements

What is the purpose of using WHERE 1=1 in SQL statements?

Yeah, it's typically because it starts out as 'where 1 = 0', to force the statement to fail.

It's a more naive way of wrapping it up in a transaction and not committing it at the end, to test your query. (This is the preferred method).

Why would someone use WHERE 1=1 AND conditions in a SQL clause?

If the list of conditions is not known at compile time and is instead built at run time, you don't have to worry about whether you have one or more than one condition. You can generate them all like:

and <condition>

and concatenate them all together. With the 1=1 at the start, the initial and has something to associate with.

I've never seen this used for any kind of injection protection, as you say it doesn't seem like it would help much. I have seen it used as an implementation convenience. The SQL query engine will end up ignoring the 1=1 so it should have no performance impact.

Why would a sql query have where 1 = 1

Was it dynamic queries? Sometimes that's helpful when building dynamic queries based on parameters that are optional.

Why the (1=1) in the Where clause?

When generating dynamic SQL from code, it can be useful to just start with a WHERE (1=1) then concatenate\append AND <Condition> as needed. Not sure if that's the case with that answer, but perhaps it was based on some code for generating SQL.

why would you use WHERE 1=0 statement in SQL?

A query like this can be used to ping the database. The clause:

WHERE 1=0

Ensures that non data is sent back, so no CPU charge, no Network traffic or other resource consumption.

A query like that can test for:

• server availability
• CUST_ATTR49 table existence
• ID column existence
• Keeping a connection alive
• Cause a trigger to fire without changing any rows (with the where clause, but not in a select query)
• manage many OR conditions in dynamic queries (e.g WHERE 1=0 OR <condition>)

Is there ever a logical reason to use 1=1 in a where clause?

It makes building dynamic WHERE clauses easier...

WHERE
  1=1
  AND condition1
  AND condition2

This way you don't have to work out if you need the AND or not as you add conditions. You always need the AND.

where 1=1 statement

It's usually when folks build up SQL statements.

When you add and value = "Toyota" you don't have to worry about whether there is a condition before or just WHERE. The optimiser should ignore it

No magic, just practical

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Example Code:

commandText = "select * from car_table where 1=1";

if (modelYear <> 0)     commandText += " and year="+modelYear
if (manufacturer <> "") commandText += " and value="+QuotedStr(manufacturer)
if (color <> "")        commandText += " and color="+QuotedStr(color)
if (california)         commandText += " and hasCatalytic=1"

Otherwise you would have to have a complicated set of logic:

commandText = "select * from car_table"
whereClause = "";
if (modelYear <> 0)
{
   if (whereClause <> "") 
      whereClause = whereClause + " and ";
   commandText += "year="+modelYear;
}
if (manufacturer <> "")
{    
   if (whereClause <> "") 
      whereClause = whereClause + " and ";
   commandText += "value="+QuotedStr(manufacturer)
}
if (color <> "")
{
   if (whereClause <> "") 
      whereClause = whereClause + " and ";
   commandText += "color="+QuotedStr(color)
}
if (california)
{
   if (whereClause <> "") 
      whereClause = whereClause + " and ";
   commandText += "hasCatalytic=1"
}

if (whereClause <> "")
   commandText = commandText + "WHERE "+whereClause;

why we are using 1 = 1 in SQL select Query

Tools often use this to let them append AND some_other_condition to the query, without having to worry whether this is the first predicate or not.

If you write

SELECT * FROM A

...and want to add a predicate you need to append "WHERE C1=1", but then adding a second predicate would append "AND C2=1"

But if you write

SELECT * FROM A WHERE 1=1

...you can just append "AND C1=1" for the first, and "AND C2=1" for the second

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