CODEWITHSUNDEEP
phpcountmysql-num-rows
Bogdan C
Bogdan C

Reputation: 399

SELECT count rows from 2 tables and sum the results

I have the PHP code:

$query = mysqli_query($mysqli, "SELECT * FROM `table_1`");
$result = mysqli_num_rows($query);

$queryTwo = mysqli_query($mysqli, "SELECT * FROM `table_2`");
$resultTwo = mysqli_num_rows($queryTwo);

$number =  $result + $resultTwo;
return $number;

The point is that sometimes, the $number variable is returning NULL, when it should not supposed to do that.

I have always rows in those 2 tables, and the returned result should not be NULL, ever.

Is this a correct approach to sum the number of rows from 2 tables? I don`t understand why sometimes I get NULL instead of a number.

Upvotes: 0

Views: 1072

Answers (2)

Allan
Allan

Reputation: 12438

Why don't you go with only one query like this: you will have the result directly in one step and it will avoid contacting the DB twice to fetch intermediate result and it will also simplify your program! 

SELECT 
(select count(*) from table_1)
+
(select count(*) from table_2)

Upvotes: 1

Muhammad Usman
Muhammad Usman

Reputation: 10148

Well, I would suggest you to do it like 

  select ( select count(*) from Table1 ) + ( select count(*) from Table2 ) 
  as total_rows

executing this query and getting the value of total_rows will return you true result

Or you can create a stored procedure to do the same thing. as explained below

CREATE PROCEDURE sp_Test
AS
-- Create two integer values
DECLARE @tableOneCount int, @tableTwoCount int

-- Get the number of rows from the first table
SELECT @tableOneCount = (SELECT COUNT(*) FROM Table1
                         WHERE WhereClause)
SELECT @tableTwoCount = (SELECT COUNT(*) FROM Table2
                         WHERE WhereClause)

-- Return the sum of the two table sizes
SELECT TotalCount = @tableOneCount + @tableTwoCount

Upvotes: 3

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