learning-oracle-how2j
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-- 别名示例 SELECT salary*12 AS "年薪" FROM hr.employees;
-- 字符串拼接示例 SELECT first_name || ‘ ‘ || last_name AS "姓名" FROM hr.employees;
-- 消除重复行 SELECT DISTINCT department_id AS "部门号" FROM hr.employees;
-- 条件限定语句 SELECT * FROM hr.employees WHERE salary >= 20000; SELECT * FROM hr.employees WHERE salary BETWEEN 3000 AND 4000; SELECT * FROM hr.employees WHERE salary IN (3000,5000); SELECT * FROM hr.employees WHERE first_name LIKE ‘%a_‘; SELECT * FROM hr.employees WHERE department_id IS NULL;
-- 逻辑条件 SELECT * FROM hr.employees WHERE salary>=3000 AND salary<=5000; SELECT * FROM hr.employees WHERE first_name LIKE ‘_a%‘ OR first_name LIKE ‘%a_‘; SELECT * FROM hr.employees WHERE first_name NOT LIKE ‘%a_‘;
-- 排序查询 SELECT e.first_name || ‘ ‘ || e.last_name AS "姓名", e.salary AS "年薪" FROM hr.employees e ORDER BY e.salary DESC;
-- 关联查询 SELECT e.first_name || ‘ ‘ || e.last_name AS "姓名", d.department_name AS "部门名称" FROM hr.employees e LEFT JOIN hr.departments d ON e.department_id = d.department_id;
-- 统计查询 SELECT AVG(salary) FROM hr.employees;
-- 分页查询SELECT * FROM ( SELECT ROWNUM r,e1.* FROM( SELECT * FROM hr.employees e ORDER BY e.salary DESC )e1 )WHERE r > 4 AND r < 11;
(编辑:李大同)
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