sql数据库函数例子

SELECT CONCAT('Hello', ' ', 'World') AS greeting;

greeting
----------------
Hello World

SELECT UPPER('hello world') AS uppercased;

uppercased
----------------
HELLO WORLD

SELECT ABS(-10) AS absolute_value;

absolute_value
----------------
10

SELECT ROUND(3.14159, 2) AS rounded_value;

rounded_value
----------------
3.14

SELECT NOW() AS current_datetime;

current_datetime
-------------------------
2023-10-05 12:34:56

SELECT DATE_ADD(NOW(), INTERVAL 1 DAY) AS tomorrow;

tomorrow
-------------------------
2023-10-06 12:34:56

SELECT COUNT(*) AS total_rows FROM users;

total_rows
----------------
100

SELECT SUM(salary) AS total_salary FROM employees;

total_salary
----------------
500000

SELECT name,
       CASE
           WHEN age < 18 THEN 'Minor'
           ELSE 'Adult'
       END AS age_group
FROM users;

name    | age_group
-------------------------
Alice   | Adult
Bob     | Minor
Charlie | Adult