I have a table with ids they read '0050001B' and such then there is '50001B'. They are both the same but due to the fact that I'm using char when I want to return something it sees both as two different ids. Is there anyway to update the table such that I can get rid of the leading zero.
I used this code below to output without leading zeros, but I want to fix the table.
SELECT TRIM(LEADING '0' FROM id) FROM mytable;
but i want to fix the table so the zeros are gone on the table, not just on the output.
any help is greatly appreciated!!
you should use update.
update mytable
set id = TRIM(LEADING '0' FROM id);
Related
I wanted to create a query in MYSQL that would trim the leading '# ' from all of the fields in a column.
update values set value = TRIM(LEADING '# ' from value)
However, doing this gives me an error
Duplicate entry '3002' for key value
The value column has a unique constraint and the error probably occurs because the query is trying to set the same value to all of value column after trimming.
Is there a way to do trim leading and update in mysql?
This query looks fine.
The issue might be here. Let me give you an example.
Case 1:
At row-x, you have value '#info' and at row-y you have info.
You removed the # from row-x in your query. Now you have already info value at row-y. You can not update the new value to info as it is there already.
I would suggest either to remove the UNIQUE constraint or you do not update the database itself. You can trim with your backend programming.
This is not setting all values to the same value, this is where once trimmed you now have two different rows with the same value for that column.
To find this:
SELECT id, value, TRIM(LEADING '# ' from value) AS trimmed_value ORDER BY trimmed_value
Presuming you have some kind of id column you'll be able to find any rows where trimmed_value is identical.
I have an insert that uses a GROUP_CONCAT. In certain scenarios, the insert fails with Row XX was cut by GROUP_CONCAT. I understand why it fails but I'm looking for a way to have it not error out since the insert column is already smaller than the group_concat_max_len. I don't want to increase group_concat_max_len.
drop table if exists a;
create table a (x varchar(10), c int);
drop table if exists b;
create table b (x varchar(10));
insert into b values ('abcdefgh');
insert into b values ('ijklmnop');
-- contrived example to show that insert column size varchar(10) < 15
set session group_concat_max_len = 15;
insert into a select group_concat(x separator ', '), count(*) from b;
This insert produces the error Row 2 was cut by GROUP_CONCAT().
I'll try to provide a few clarifications -
The data in table b is unknown. There is no way to say set group_concat_max_len to a value greater than 18.
I do know the insert column size.
Why group_concat 4 GB of data when you want the first x characters?
When the concatenated string is longer than 10 chars, it should insert the first 10 characters.
Thanks.
Your example GROUP_CONCAT is probably cooking up this value:
abcdefgh, ijklmnop
That is 18 characters long, including the separator.
Can you try something like this?
set session group_concat_max_len = 4096;
insert into a
select left(group_concat(x separator ', '),10),
count(*)
from b;
This will trim the GROUP_CONCAT result for you.
You temporarily can set the group_concat_max_len if you need to, then set it back.
I don't know MySQL very well, nor if there is a good reason to do this in the first place, but you could create a running total length, and limit the GROUP_CONCAT() to where that length is under a certain max, you'll still need to set your group_concat_max_len high enough to handle the longest single value (or utilize CASE logic to substring them to be under the max length you desire.
Something like this:
SELECT SUBSTRING(GROUP_CONCAT(col1 separator ', '),1,10)
FROM (SELECT *
FROM (SELECT col1
,#lentot := COALESCE(#lentot,0) + CHAR_LENGTH(col1) AS lentot
FROM Table1
)sub
WHERE lentot < 25
)sub2
Demo: SQL Fiddle
I don't know if it's SQL Fiddle being quirky or if there's a problem with the logic, but sometimes when running I get no output. Not big on MySQL so could definitely be me missing something. It doesn't seem like it should require 2 subqueries but filtering didn't work as expected unless it was nested like that.
Actually, a better way is to use DISTINCT.
I had a situation to add new two fields into existing stored procedure, in a way that a value for that new fields had been obtained by a LEFT JOIN, and because it may have contained a NULL value, a single "concat" value was multiplicated for some cases more than a 100 times.
Because, a group with that new field value contained many NULL values, GROUP_CONCAT exceeded maximum value (in my case 16384).
I'm trying to create a simple table where I insert field and I do some checks in MySql. I've used Microsoft SQL relatively easy. Instead, MySql give evrrytime query errors without even specifying what's going on. Poor MySql software design apart, here's what I'm trying to do:
1 table with 4 fields with an autoincremental autogenerated number to det an ID as primary key
CREATE TABLE `my_db`.`Patients_table` (
`ID_Patient` INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY ,
`Patient_name` VARCHAR( 200 ) NOT NULL ,
`Recovery_Date` DATETIME NOT NULL ,
`Recovery_count` INT NOT NULL
) ENGINE = MYISAM
a simple stored procedure to insert such fields and check if something exist before inserting:
CREATE PROCEDURE nameInsert(IN nome, IN data)
INSERT INTO Patients_table (Patient_name,Recovery_Date) values (nome,data)
IF (EXISTS (SELECT Recovery_count FROM Tabella_nomi) = 0) THEN
INSERT INTO (Patients_table (Recovery_count)
ELSE
SET Recovery_count = select Recovery_count+1 from Patients_table
END
this seems wrong on many levels and MySQL useless syntax checker does not help.
How can I do this? Thanks.
There seems to be a lot wrong with this block of code. (No offense intended!)
First, Procedures need to be wrapped with BEGIN and END:
CREATE PROCEDURE nameInsert(IN nome, IN data)
BEGIN
...[actually do stuff here]
END
Second, since your table is declared with all fields as NOT NULL, you must insert all fields with an INSERT statement (this includes the Recovery_Date column, and excludes the AUTO_INCREMENT column). You can add DEFAULT CURRENT_TIMESTAMP to the date column if you want it to be set automatically.
INSERT INTO Patients_table (Patient_name,Recovery_Date) values (nome,data)
Third, what exactly is your IF predicate doing?
EXISTS (SELECT Recovery_count FROM Tabella_nomi) = 0
If you want to check if a row exists, don't put the = 0 at the end. Also, Tabella_nomi isn't declared anywhere in that procedure. Also, your SELECT statement should have a WHERE clause, since I'm assuming you want to select a specific row (this is going to select a result set of all recovery_counts).
Fourth, the second INSERT statement seems a little messy. It should look more like the first INSERT, and keep the point I made above in mind.
INSERT INTO (Patients_table (Recovery_count)
Fifth, the ELSE statement
SET Recovery_count = select Recovery_count+1 from Patients_table
Has some problems too. SET is meant for setting variables, not values in rows. I'm not 100% sure what your intent is from this statement, but it looks like you meant to increment the Recovery_count column of a certain row if it already exists. In which case, you meant to do something like this:
UPDATE Patients_table SET Recovery_count = Recovery_count+1 WHERE <conditional predicate>
Where the conditional predicate is something like this:
Patients_name = nome
Try these things, and look at the errors it gives you when you try to execute the CREATE STATEMENT. I bet they're more useful then you think!
I have a column that contains string. It is a number but saved as string. The string might start with 00 or more than two zeros. I need to remove the zeros and insert the new value (after removing) into another column. The problem is the number of zeros at the beginning is not fixed. It can be 2 or more. Is this task possible to be done with MySQL ? How?
A good hint is provided here:
UPDATE your_table
SET column2 = TRIM(LEADING '0' FROM column1)
supposing that the original value is stored in column1 and you want to write the 0-trimmed one in column2
you can use CONVERT(col,UNSIGNED INTEGER) to convert it into the number, that should remove the leading zeros.
query can be
insert into <table> values(select CONVERT(col,UNSIGNED INTEGER),..... from <table2>);
Using MySQL 5.1.49, I'm trying to implement a tagging system
the problem I have is with a table with two columns: id(autoincrement), tag(unique varchar) (InnoDB)
When using query, INSERT IGNORE INTO tablename SET tag="whatever", the auto increment id value increases even if the insert was ignored.
Normally this wouldn't be a problem, but I expect a lot of possible attempts to insert duplicates for this particular table which means that my next value for id field of a new row will be jumping way too much.
For example I'll end up with a table with say 3 rows but bad id's
1 | test
8 | testtext
678 | testtextt
Also, if I don't do INSERT IGNORE and just do regular INSERT INTO and handle the error, the auto increment field still increases so the next true insert is still a wrong auto increment.
Is there a way to stop auto increment if there's an INSERT duplicate row attempt?
As I understand for MySQL 4.1, this value wouldn't increment, but last thing I want to do is end up either doing a lot of SELECT statements in advance to check if the tags exist, or worse yet, downgrade my MySQL version.
You could modify your INSERT to be something like this:
INSERT INTO tablename (tag)
SELECT $tag
FROM tablename
WHERE NOT EXISTS(
SELECT tag
FROM tablename
WHERE tag = $tag
)
LIMIT 1
Where $tag is the tag (properly quoted or as a placeholder of course) that you want to add if it isn't already there. This approach won't even trigger an INSERT (and the subsequent autoincrement wastage) if the tag is already there. You could probably come up with nicer SQL than that but the above should do the trick.
If your table is properly indexed then the extra SELECT for the existence check will be fast and the database is going to have to perform that check anyway.
This approach won't work for the first tag though. You could seed your tag table with a tag that you think will always end up being used or you could do a separate check for an empty table.
I just found this gem...
http://www.timrosenblatt.com/blog/2008/03/21/insert-where-not-exists/
INSERT INTO [table name] SELECT '[value1]', '[value2]' FROM DUAL
WHERE NOT EXISTS(
SELECT [column1] FROM [same table name]
WHERE [column1]='[value1]'
AND [column2]='[value2]' LIMIT 1
)
If affectedRows = 1 then it inserted; otherwise if affectedRows = 0 there was a duplicate.
The MySQL documentation for v 5.5 says:
"If you use INSERT IGNORE and the row is ignored, the AUTO_INCREMENT counter
is **not** incremented and LAST_INSERT_ID() returns 0,
which reflects that no row was inserted."
Ref: http://dev.mysql.com/doc/refman/5.5/en/information-functions.html#function_last-insert-id
Since version 5.1 InnoDB has configurable Auto-Increment Locking. See also http://dev.mysql.com/doc/refman/5.1/en/innodb-auto-increment-handling.html#innodb-auto-inc...
Workaround: use option innodb_autoinc_lock_mode=0 (traditional).
I found mu is too short's answer helpful, but limiting because it doesn't do inserts on an empty table. I found a simple modification did the trick:
INSERT INTO tablename (tag)
SELECT $tag
FROM (select 1) as a #this line is different from the other answer
WHERE NOT EXISTS(
SELECT tag
FROM tablename
WHERE tag = $tag
)
LIMIT 1
Replacing the table in the from clause with a "fake" table (select 1) as a allowed that part to return a record which allowed the insert to take place. I'm running mysql 5.5.37. Thanks mu for getting me most of the way there ....
The accepted answer was useful, however I ran into a problem while using it that basically if your table had no entries it would not work as the select was using the given table, so instead I came up with the following, which will insert even if the table is blank, it also only needs you to insert the table in 2 places and the inserting variables in 1 place, less to get wrong.
INSERT INTO database_name.table_name (a,b,c,d)
SELECT
i.*
FROM
(SELECT
$a AS a,
$b AS b,
$c AS c,
$d AS d
/*variables (properly escaped) to insert*/
) i
LEFT JOIN
database_name.table_name o ON i.a = o.a AND i.b = o.b /*condition to not insert for*/
WHERE
o.a IS NULL
LIMIT 1 /*Not needed as can only ever be one, just being sure*/
Hope you find it useful
You can always add ON DUPLICATE KEY UPDATE Read here (not exactly, but solves your problem it seems).
From the comments, by #ravi
Whether the increment occurs or not depends on the
innodb_autoinc_lock_mode setting. If set to a non-zero value, the
auto-inc counter will increment even if the ON DUPLICATE KEY fires
I had the same problem but didn't want to use innodb_autoinc_lock_mode = 0 since it felt like I was killing a fly with a howitzer.
To resolve this problem I ended up using a temporary table.
create temporary table mytable_temp like mytable;
Then I inserted the values with:
insert into mytable_temp values (null,'valA'),(null,'valB'),(null,'valC');
After that you simply do another insert but use "not in" to ignore duplicates.
insert into mytable (myRow) select mytable_temp.myRow from mytable_temp
where mytable_temp.myRow not in (select myRow from mytable);
I haven't tested this for performance, but it does the job and is easy to read. Granted this was only important because I was working with data that was constantly being updated so I couldn't ignore the gaps.
modified the answer from mu is too short, (simply remove one line)
as i am newbie and i cannot make comment below his answer. Just post it here
the query below works for the first tag
INSERT INTO tablename (tag)
SELECT $tag
WHERE NOT EXISTS(
SELECT tag
FROM tablename
WHERE tag = $tag
)
I just put an extra statement after the insert/update query:
ALTER TABLE table_name AUTO_INCREMENT = 1
And then he automatically picks up the highest prim key id plus 1.