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POSQL SELECT query with multiple conditions
 

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    <p>I'm stuck with a SQL query. Let's say we have an employee, a task table and a many to many association between them. The tables look like this:</p> <pre><code>employees id|name 1 | John 2 | Peter 3 | Mike tasks id | name 1 | Support 2 | Programming 3 | Call customers 4 | Write Newsletters 5 | Write Invoices employees_tasks employee_id | task_id 1 | 1 1 | 2 2 | 3 2 | 4 2 | 5 3 | 2 </code></pre> <p>Now I want to get all employees, who have "Programming" as their tasks. The correct query is:</p> <pre><code>SELECT employees.id, employees.name FROM employees INNER JOIN employees_tasks ON employees.id = employees_tasks.employee_id INNER JOIN tasks ON employees_tasks.task_id = tasks.id WHERE tasks.name LIKE 'Programming' </code></pre> <p>So far so good... But now I want to get all employees, whose tasks are "Programming" <em>and</em> "Support". This query gives me NULL:</p> <pre><code>SELECT employees.id, employees.name FROM employees INNER JOIN employees_tasks ON employees.id = employees_tasks.employee_id INNER JOIN tasks ON employees_tasks.task_id = tasks.id WHERE tasks.name LIKE 'Programming' AND tasks.name LIKE 'Support' </code></pre> <p>I receive three records with this query</p> <pre><code>SELECT employees.id, employees.name FROM employees INNER JOIN employees_tasks ON employees.id = employees_tasks.employee_id INNER JOIN tasks ON employees_tasks.task_id = tasks.id WHERE tasks.name IN ('Programming', 'Support') </code></pre> <p>2x John and 1x Mike. But that's not what I want. I want all employees, who have the tasks "Programming" AND "Support" - not those, who only have one of the tasks.</p> <p>There's another option. I use ALL with a subquery. Here we go:</p> <pre><code>SELECT employees.id, employees.name FROM employees INNER JOIN employees_tasks ON employees.id = employees_tasks.employee_id INNER JOIN tasks ON employees_tasks.task_id = tasks.id WHERE tasks.name = ALL (SELECT DISTINCT name FROM tasks WHERE name LIKE 'Programming' OR name LIKE 'Support') </code></pre> <p>But I receive with this query NULL, although there is an employee, who have both tasks: John!</p> <p>How can I implement such a query?</p> <p>Best Regards Christian</p>
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