mysql sql99 Intra syntax Connections Non equivalent Connections Detailed Explanation

# Case: Query Employee's Salary Grade

SELECT
  salary,grade_level
FROM
  employees e
JOIN
  job_grades g
ON
  e.`salary` BETWEEN g.`lowest_sal` AND g.`lowest_sal`;

# Case: Query the number of salary grades in descending order

SELECT
  COUNT(*),grade_level
FROM
  job_grades j
JOIN
  employees e
ON
  e.`salary` BETWEEN j.`lowest_sal`AND j.`highest_sal`
GROUP BY
  grade_level DESC;

Content extension:

Grammar

select Query List

from Table 1 Alias [Connection Type]

jion Table 2 Alias

on Connection Condition

[where Filter Criteria]

[group by Packet]

[having Filter Criteria]

[order by Sort List]

Case 1: Query employee name and department name

SELECT last_name,department_name
FROM employees e
INNER JOIN departments d
ON e.department_id=d.department_id;

Case 2: Query the name of the employee and job with e (add filter)

SELECT last_name,job_title
FROM employees e
INNER JOIN jobs j
ON e.job_id=j.job_id
WHERE e.last_name LIKE  ' %e%';

These are all the knowledge points introduced this time.