MySQL和达梦数据库SQL语法差异对比示例总结

CREATE TABLE order_info_mysql (
    id        BIGINT PRIMARY KEY AUTO_INCREMENT,
    amount    DECIMAL(18, 2),
    discount  FLOAT
);

CREATE TABLE order_info_dm (
    id        BIGINT PRIMARY KEY,
    amount    NUMBER(18, 2),
    discount  NUMBER(10, 4)
);

CREATE TABLE user_mysql (
    id       BIGINT PRIMARY KEY AUTO_INCREMENT,
    name     VARCHAR(50),
    bio      TEXT
);

CREATE TABLE user_dm (
    id       BIGINT PRIMARY KEY,
    name     VARCHAR2(50),
    bio      CLOB
);

SELECT NOW(), CURDATE();

SELECT SYSDATE, CURRENT_DATE FROM DUAL;

CREATE TABLE user_mysql (
    id   BIGINT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(50)
);

INSERT INTO user_mysql (name) VALUES ('Tom');

CREATE TABLE user_dm_identity (
    id   BIGINT IDENTITY(1,1) PRIMARY KEY,
    name VARCHAR2(50)
);

INSERT INTO user_dm_identity (name) VALUES ('Tom');

CREATE SEQUENCE seq_user_dm
    START WITH 1
    INCREMENT BY 1;

CREATE TABLE user_dm (
    id   BIGINT PRIMARY KEY,
    name VARCHAR2(50)
);

INSERT INTO user_dm (id, name)
VALUES (seq_user_dm.NEXTVAL, 'Tom');

SELECT * FROM user_mysql
ORDER BY id
LIMIT 10 OFFSET 20;  -- 从第21行开始，取10行

SELECT * FROM user_mysql
ORDER BY id
LIMIT 20, 10;        -- 同样效果

SELECT *
FROM (
    SELECT u.*, ROWNUM AS rn
    FROM user_dm u
    ORDER BY u.id
) t
WHERE t.rn > 20 AND t.rn <= 30;

SELECT *
FROM (
    SELECT u.*, ROW_NUMBER() OVER (ORDER BY u.id) AS rn
    FROM user_dm u
) t
WHERE t.rn > 20 AND t.rn <= 30;

SELECT CONCAT(first_name, ' ', last_name) AS full_name
FROM user_mysql
WHERE INSTR(name, 'Tom') > 0;

SELECT first_name || ' ' || last_name AS full_name
FROM user_dm
WHERE INSTR(name, 'Tom') > 0;

SELECT DATE_FORMAT(NOW(), '%Y-%m-%d %H:%i:%s') AS now_str;

SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD HH24:MI:SS') AS now_str
FROM DUAL;

INSERT INTO logs_mysql (create_time)
VALUES (STR_TO_DATE('2024-01-01 10:20:30', '%Y-%m-%d %H:%i:%s'));

INSERT INTO logs_dm (create_time)
VALUES (TO_DATE('2024-01-01 10:20:30', 'YYYY-MM-DD HH24:MI:SS'));

SELECT IFNULL(nickname, '匿名') AS nick
FROM user_mysql;

SELECT NVL(nickname, '匿名') AS nick
FROM user_dm;

SELECT
    IF(status = 1, '启用', '禁用') AS status_name
FROM user_mysql;

SELECT
    CASE WHEN status = 1 THEN '启用' ELSE '禁用' END AS status_name
FROM user_dm;

SELECT
    DECODE(status, 1, '启用', '禁用') AS status_name
FROM user_dm;

SHOW TABLES;

SELECT TABLE_NAME
FROM USER_TABLES;

SELECT OWNER, TABLE_NAME
FROM ALL_TABLES;

DESC user_mysql;
-- 或
SHOW COLUMNS FROM user_mysql;

SELECT COLUMN_NAME, DATA_TYPE, DATA_LENGTH, NULLABLE
FROM USER_TAB_COLUMNS
WHERE TABLE_NAME = 'USER_DM';

-- 开启事务（MySQL + InnoDB & 达梦）
START TRANSACTION;

UPDATE account SET balance = balance - 100 WHERE id = 1;
UPDATE account SET balance = balance + 100 WHERE id = 2;

COMMIT;  -- 或 ROLLBACK;

CREATE TABLE user_mysql (
    id     BIGINT PRIMARY KEY AUTO_INCREMENT,
    email  VARCHAR(100) UNIQUE
);

CREATE UNIQUE INDEX idx_user_email
ON user_mysql (email);

CREATE TABLE user_dm (
    id     BIGINT PRIMARY KEY,
    email  VARCHAR2(100),
    CONSTRAINT uk_user_email UNIQUE (email)
);

CREATE UNIQUE INDEX idx_user_email
ON user_dm (email);

CREATE TABLE order_mysql (
    id         BIGINT PRIMARY KEY AUTO_INCREMENT,
    user_id    BIGINT,
    CONSTRAINT fk_order_user
        FOREIGN KEY (user_id) REFERENCES user_mysql(id)
);

CREATE TABLE order_dm (
    id         BIGINT PRIMARY KEY,
    user_id    BIGINT,
    CONSTRAINT fk_order_user
        FOREIGN KEY (user_id) REFERENCES user_dm(id)
);

SELECT id, name, age
FROM user_mysql
WHERE age >= 18
ORDER BY create_time DESC
LIMIT 20, 10;

SELECT *
FROM (
    SELECT
        u.id,
        u.name,
        u.age,
        ROW_NUMBER() OVER (ORDER BY u.create_time DESC) AS rn
    FROM user_dm u
    WHERE u.age >= 18
) t
WHERE t.rn > 20 AND t.rn <= 30;

SELECT
    DATE_FORMAT(create_time, '%Y-%m-%d') AS dt,
    COUNT(*) AS cnt
FROM user_mysql
GROUP BY DATE_FORMAT(create_time, '%Y-%m-%d')
ORDER BY dt;

SELECT
    TO_CHAR(create_time, 'YYYY-MM-DD') AS dt,
    COUNT(*) AS cnt
FROM user_dm
GROUP BY TO_CHAR(create_time, 'YYYY-MM-DD')
ORDER BY dt;

SELECT
    SUM(IF(status = 1, 1, 0)) AS active_cnt,
    SUM(IF(status = 0, 1, 0)) AS inactive_cnt
FROM user_mysql;

SELECT
    SUM(CASE WHEN status = 1 THEN 1 ELSE 0 END) AS active_cnt,
    SUM(CASE WHEN status = 0 THEN 1 ELSE 0 END) AS inactive_cnt
FROM user_dm;