mysql修改重複字段

Question

我有一個表（產品）有重複的products_model字段。 我需要將它們更改爲一些新的值。 我可以選擇他們：SELECT * FROM products GROUP BY products_model HAVING count(*) >=2

我需要改變products_model = products_model + RANDOM NUMBER

謝謝

Answer 1

鑑於這兩個領域是VARCHAR處理這樣做的工作，串聯products_model並用下劃線

update products p1, 
    products p2 
set 
    p1.products_model = concat(p1.products_model, '_', p1.products_id), 
    p2.products_model = concat(p2.products_model, '_', p2.products_id) 
where 
    p1.products_model = p2.products_model 
     and p1.products_id > p2.products_id 

products_id

之前：

id products_model products_id 
1 A a 
2 A b 
3 B a 
4 C a 
5 C b 

後：

id products_model products_id 
1 A_a a 
2 A_b b 
3 B a 
4 C_a a 
5 C_b b 

Answer 2

這將使用變量分配一個序列號，產品具有相同的模型。然後，它會更新除第一個以外的所有型號，以便在型號名稱後面顯示序列號：

update products p join 
     (select p.*, 
       (@rn := if(@pm = products_model, @rn + 1, 
          if(@pm := products_model, 1, 1) 
         ) 
       ) as seqnum 
     from products p 
     order by products_model 
     ) pp 
     on p.id = pp.id cross join 
     (select @pm := '', @rn := 0) vars 
    set products_model = concat_ws('_', products_model, seqnum) 
    where seqnum > 1;