Get emp_no for all non-manager employees

CREATE TABLE `dept_manager` (
`dept_no` char(4) NOT NULL,
`emp_no` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL.PRIMARY KEY (`emp_no`,`dept_no`));
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CREATE TABLE `employees` (
`emp_no` int(11) NOT NULL,
`birth_date` date NOT NULL,
`first_name` varchar(14) NOT NULL,
`last_name` varchar(16) NOT NULL,
`gender` char(1) NOT NULL,
`hire_date` date NOT NULL.PRIMARY KEY (`emp_no`));
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01 I to answer

An inner join is the intersection of two tables. Select * from B where table A and table B are NULL; select * from B where table A and table B are NULL;

select t1.emp_no
from employees t1
left join dept_manager t2 on t1.emp_no = t2.emp_no
where t2.emp_no is null
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02 to you to review

  • left join + is NULL
select t1.emp_no
from employees t1
left join dept_manager t2 on t1.emp_no = t2.emp_no
where t2.emp_no is null
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  • Not IN
select emp_no
from employees
where emp_no not in(select emp_no from dept_manager)
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03 Today’s Knowledge

Left JOIN + is NULL not in

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