Question

我在MySQL中有一个名为ZipCode的表，其字段为：id，zipcode，city，state。它有一些重复的记录;一些邮政编码显示两次我想删除所有两次的zipcodes;每个邮政编码只能存储一次。我怎样才能使它正确？

Answer 1

-- remove duplicates

DELETE z1
FROM ZipCode z1, ZipCode z2
WHERE z1.zipcode = z2.zipcode AND z2.id < z1.id;

-- add a primary key

ALTER TABLE ZipCode ADD PRIMARY KEY (zipcode);

-- or a unique key

ALTER TABLE ZipCode ADD UNIQUE INDEX zipcode_unique (zipcode);

Answer 2

这三个查询将删除所有重复项：

CREATE TABLE new_table AS SELECT * FROM old_table WHERE 1 GROUP BY zip;
DROP TABLE old_table;
RENAME TABLE new_table TO old_table;

Answer 3

试试这个工作正常

DELETE
FROM
insurance_policy_customers ipc
WHERE
ipc.id NOT IN (SELECT
min(ipc.id)
FROM
insurance_policy_customers ipc
GROUP BY
ipc.resident_insurance_policy_id )

从表中删除重复记录

3 个答案: