SQL-basics

SQL 一些常用的查询语句用法


SQL 中的聚合函数

SQL 中的子查询

SQL 使用实例

SELECT F_NAME , L_NAME

FROM EMPLOYEES

WHERE ADDRESS LIKE '%Elgin,IL%';

SELECT F_NAME , L_NAME

FROM EMPLOYEES

WHERE B_DATE LIKE '197%';

SELECT *

FROM EMPLOYEES

WHERE (SALARY BETWEEN 60000 AND 70000) AND DEP_ID = 5;

SELECT F_NAME, L_NAME, DEP_ID

FROM EMPLOYEES

ORDER BY DEP_ID;

SELECT F_NAME, L_NAME, DEP_ID

FROM EMPLOYEES

ORDER BY DEP_ID DESC, L_NAME DESC;

SELECT D.DEP_NAME , E.F_NAME, E.L_NAME

FROM EMPLOYEES as E, DEPARTMENTS as D

WHERE E.DEP_ID = D.DEPT_ID_DEP

ORDER BY D.DEP_NAME, E.L_NAME DESC;

SELECT DEP_ID, COUNT(*)

FROM EMPLOYEES

GROUP BY DEP_ID;

SELECT DEP_ID, COUNT(*), AVG(SALARY)

FROM EMPLOYEES

GROUP BY DEP_ID;

SELECT DEP_ID, COUNT(*) AS "NUM_EMPLOYEES", AVG(SALARY) AS "AVG_SALARY"

FROM EMPLOYEES

GROUP BY DEP_ID;

SELECT DEP_ID, COUNT(*) AS "NUM_EMPLOYEES", AVG(SALARY) AS "AVG_SALARY"

FROM EMPLOYEES

GROUP BY DEP_ID

ORDER BY AVG_SALARY;

SELECT DEP_ID, COUNT() AS "NUM_EMPLOYEES", AVG(SALARY) AS "AVG_SALARY"
FROM EMPLOYEES
GROUP BY DEP_ID
HAVING count(
) < 4

ORDER BY AVG_SALARY;

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