從表中刪除重複記錄

Question

我在MySQL中有一個名爲ZipCode的表，它的字段是：id，zipcode，city，state。它有一些重複的記錄;一些郵編顯示兩次 我想刪除所有即將到來的郵編，每個郵政編碼只能存儲一次。 我如何使它正確？

Answer 1

這組三個查詢將刪除所有重複：

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 2

-- 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 3

試試這個它的做工精細

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)