Question

Hello there i am having little problem. I have two tables in my database.

As you can see i am getting all employees in one tab, and what i am trying to achieve here is to display only relevant employees in given tab. So employees from Customer services wont be displayed in Sales tab for example.

$query = mysql_query("SELECT * "."FROM employees, dept_emp "."WHERE employees.emp_no = dept_emp.emp_no");

Thank you for looking and help 🙂

Answer 1

Your WHERE clause is useless as it is just restating a JOIN condition basically. Try this:

SELECT *
FROM employees AS e
INNER JOIN dept_emp AS de ON e.emp_no = de.emp_no
WHERE de.dept_no = '?'

Obviously the ? would be substituted with the dept_no value you are actually trying to filter on.

Per your question about seeting query limits/pagination, that is done via SQL LIMIT clause. The clause can be expressed in a few different ways.

This first just returns a max number of rows:

LIMIT 100 <-- shows first 100 rows from the result set

The following two forms of syntax are used for pagination of results:

LIMIT 0, 100 <-- show first 100 rows from the result set (start at 0 offset, and return a max of 100 rows
LIMIT 100, 100 <-- show rows 101-200 from the result set (start at 100 offset and return max of 100 rows)

Or:

LIMIT 100 OFFSET 0 <-- first 100 rows
LIMIT 100 OFFSET 100 <-- rows 101-200

So putting it all together

SELECT *
FROM employees AS e
INNER JOIN dept_emp AS de ON e.emp_no = de.emp_no
WHERE de.dept_no = '?'
ORDER BY e.emp_no
LIMIT 0,100

Note that I also added an ORDER BY clause. This is important for pagination in that just a regular unordered SELECT doesn’t guarantee order. If you tried to paginate without an ORDER BY you could potentially get the same row returned in multiple “pages”.