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Posted on 2015-01-27
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Hi, I have a small mysql database and I have some corrupted data because my code was bugged. I have fixed the bug but not the corrupted data.

I need some sql to take all the duplicate values of x1 that have duplicate values of x2 and x3 and rename them to something so they are unique. If x3 is null, nothing should be done.

So this is before created with some data

mysql>
mysql> select * from test;
+------+---------+------+------+
| x0   | x1      | x2   | x3   |
+------+---------+------+------+
|    1 | test001 |    1 |    2 |
|    2 | test001 |    1 |    2 |
|    3 | test001 |    1 |    2 |
|    4 | test001 |    1 |    2 |
|    5 | test001 |    1 |    3 |
|    6 | test001 |    2 |    2 |
|    7 | test001 |    1 | NULL |
|    8 | test001 |    1 | NULL |
|    9 | test001 |    2 | NULL |
|   10 | test002 |    2 | NULL |
+------+---------+------+------+
10 rows in set (0.00 sec)

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and what I would like it to look like after execution of some sql might be (note the suffix a, b, c, d but I actually don't care what the new value is, just that it isn't test001).

+------+---------+------+------+
| x0   | x1      | x2   | x3   |
+------+---------+------+------+
|    1 | test001a|    1 |    2 |
|    2 | test001b|    1 |    2 |
|    3 | test001c|    1 |    2 |
|    4 | test001d|    1 |    2 |
|    5 | test001 |    1 |    3 |
|    6 | test001 |    2 |    2 |
|    7 | test001 |    1 | NULL |
|    8 | test001 |    1 | NULL |
|    9 | test001 |    2 | NULL |
|   10 | test002 |    2 | NULL |
+------+---------+------+------+

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I have created the test data with the following sql


create table test(x0 int, x1 varchar(10), x2 int, x3 int);

insert into test(x0, x1, x2, x3)
 values(1, 'test001', 1, 2);
insert into test(x0, x1, x2, x3)
 values(2, 'test001', 1, 2);
insert into test(x0, x1, x2, x3)
 values(3, 'test001', 1, 2);
insert into test(x0, x1, x2, x3)
 values(4, 'test001', 1, 2);
insert into test(x0, x1, x2, x3)
 values(5, 'test001', 1, 3);
insert into test(x0, x1, x2, x3)
 values(6, 'test001', 2, 2);
insert into test(x0, x1, x2, x3)
 values(7, 'test001', 1, null);
insert into test(x0, x1, x2, x3)
 values(8, 'test001', 1, null);
insert into test(x0, x1, x2, x3)
 values(9, 'test001', 2, null);
insert into test(x0, x1, x2, x3)
 values(10, 'test002', 2, null);

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What I don't want is a solution that relies on me executing a zillion statements like

update test set x1=test001a' where x0=1; 

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etc

because this is contrived data. In the real data I don't want to look at it first, I just want to run the sql and for it to work out the duplicates, not have be pre-identify them and know the x0 id's.

Thank you

John
0
Comment
Question by:John Bolter
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4 Comments
 
LVL 32

Expert Comment

by:Daniel Wilson
ID: 40573715
Shamelessly citing point 10 of my own article ... :) ... http://www.experts-exchange.com/Database/MySQL/A_659-Database-Developers'-Quick-Reference-to-MySQL.html

update `test` t1 inner join `test` t2 on t1.x1 = t2.x1 and t1.x2 = t2.x2 and t1.x3 is not null AND  t1.x0 <> t2.x0
set t1.x1 = concat(t1.x1,'-',t1.x0)

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0
 

Author Comment

by:John Bolter
ID: 40573756
Thanks, it's almost right. When I execute this it gives me

mysql> select * from test;
+------+-----------+------+------+
| x0   | x1        | x2   | x3   |
+------+-----------+------+------+
|    1 | test001-1 |    1 |    2 |
|    2 | test001-2 |    1 |    2 |
|    3 | test001-3 |    1 |    2 |
|    4 | test001-4 |    1 |    2 |
|    5 | test001-5 |    1 |    3 |
|    6 | test001-6 |    2 |    2 |
|    7 | test001   |    1 | NULL |
|    8 | test001   |    1 | NULL |
|    9 | test001   |    2 | NULL |
|   10 | test002   |    2 | NULL |
+------+-----------+------+------+
10 rows in set (0.00 sec)

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but the ones with x0 = 5 and x0=6 shouldn't be updated but they are.
0
 
LVL 32

Accepted Solution

by:
Daniel Wilson earned 2000 total points
ID: 40573775
Oops, I messed up the x3 condition.
update `test` t1 inner join `test` t2 on 
 t1.x1 = t2.x1 and t1.x2 = t2.x2 and t1.x3 =t3.x3
   AND  t1.x0 <> t2.x0
set t1.x1 = concat(t1.x1,'-',t1.x0)

Open in new window

0
 

Author Comment

by:John Bolter
ID: 40573786
Changed it to
and t1.x3 =t2.x3

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and it works exactly right.
Thanks Daniel
0

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