MySQL实现去重的几种方法小结

SELECT DISTINCT equipment_no
FROM equipment_check_order;

SELECT equipment_no
FROM equipment_check_order
GROUP BY equipment_no;

-- 创建目标表
CREATE TABLE IF NOT EXISTS deduplicated_orders (
    equipment_no VARCHAR(255),
    check_date DATE,
    PRIMARY KEY (equipment_no, check_date)
);

-- 将去重后的数据插入到目标表
INSERT INTO deduplicated_orders (equipment_no, check_date)
SELECT equipment_no, check_date
FROM equipment_check_order AS e
WHERE check_date = (
    SELECT MAX(check_date)
    FROM equipment_check_order
    WHERE equipment_no = e.equipment_no
);

-- 创建目标表
CREATE TABLE IF NOT EXISTS deduplicated_orders (
    equipment_no VARCHAR(255),
    check_date DATE,
    PRIMARY KEY (equipment_no, check_date)
);

-- 使用自联接将去重后的数据插入到目标表
INSERT INTO deduplicated_orders (equipment_no, check_date)
SELECT e1.equipment_no, e1.check_date
FROM equipment_check_order e1
LEFT JOIN equipment_check_order e2
ON e1.equipment_no = e2.equipment_no
AND e1.check_date < e2.check_date
WHERE e2.check_date IS NULL;

-- 创建目标表（如果不存在）
CREATE TABLE IF NOT EXISTS deduplicated_orders (
    equipment_no VARCHAR(255),
    check_date DATE,
    PRIMARY KEY (equipment_no, check_date)
);

-- 使用 CTE 和 ROW_NUMBER() 进行去重
WITH ranked AS (
  SELECT equipment_no,
         check_date,
         ROW_NUMBER() OVER (PARTITION BY equipment_no ORDER BY check_date DESC) AS rn
  FROM equipment_check_order
)
INSERT INTO deduplicated_orders (equipment_no, check_date)
SELECT equipment_no, check_date
FROM ranked
WHERE rn = 1;