This question already has answers here:
How to get the next auto-increment id in mysql
(21 answers)
Closed 9 years ago.
I am using MySQL.
I want to retrieve the next value that the AUTO_INCREMENT column will take without entering a new record.
create table ABC(id int(10) NOT NULL AUTO_INCREMENT,name char(10));
In oracle I would have used sequencename.nextval(); But what to I use in MySQL?
Here is why I did not use
select max(id) from ABC;
Suppose I have an entry with id=2. Now column id will take the next value as 3.
Before I create a record with id=3, If I delete the record with id=2.
The answer for query I mentioned will be 2. But I want the actual value 3, which the auto_increment column will anyway take.
Query table status like this:
SHOW TABLE STATUS WHERE `Name` = 'table_name'
Now in result you will get a column named Auto_increment. This is the value You were asking for.
In JAVA:
conn = DriverManager.getConnection(connectionUrl, connectionUser, connectionPassword);
stmt = conn.createStatement();
rs = stmt.executeQuery("SHOW TABLE STATUS WHERE `Name` = 'table_name'");
rs.next();
String nextid = rs.getString("Auto_increment");
Full example here: http://www.avajava.com/tutorials/lessons/how-do-i-use-jdbc-to-query-a-mysql-database.html
If I understand correctly,you could use the number of rows as indicator:
SELECT TABLE_ROWS+1
FROM information_schema.tables
WHERE table_name='tableName'
AND table_schema = DATABASE();
There is no way to guarantee what value you are going to get before inserting the row. This is mostly because you will have to lock the entire table to guarantee no other thread will do an insert with "your" next value.
You can reserve a value by starting a transaction, inserting a row, getting the value and then doing a rollback. Then you can safely use that value.
It will be much simpler to just insert the row, so maybe I'm not understanding the purpose of what you are doing.
Related
I'm trying to put the number of id in the neighbor column. Something like this:
+----+-------------------+
| id | identical_with_id |
+----+-------------------+
id is AUTO INCREMENT and all need is getting id's number when inserting. I can do that like this:
INSERT INTO `table_name`
VALUES( NULL,
(SELECT `AUTO_INCREMENT` FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA = 'database_name' AND
TABLE_NAME = 'table_name')
);
But I don't know it will work all the time. Maybe between executing that sub-query and inserting that row, a new row (another row) get insert. In this case the number of id will not be the same as neighbor column. Hum? is that possible?
Note: Please don't tell me: "what do you need this for?"
Usually everyone sometimes need to do such things. And it's best to not ask for reasons :)
I think you are doing it in correct way but you need to check which MySql engine you are using and make sure that inserts are executed sequentially.
Usually insert statement will lock the table and unlock when it's finished. That means your query for retrieving auto increment is pretty much safe.
For MySql engine and related settings this post can help you:
Does a MySQL multi-row insert grab sequential autoincrement IDs?
For InnoDb:
http://dev.mysql.com/doc/refman/5.1/en/innodb-auto-increment-handling.html
You could use LAST_INSERT_ID() right after your query.
INSERT INTO `table_name` VALUES( NULL, NULL);
SELECT LAST_INSERT_ID() INTO #last_id;
UPDATE `table_name` SET duplicate_id_column = #last_id WHERE id = #last_id;
I have a table with primary key (its name is "id") defined as auto_increment. I use NULL in INSERT statements to "fill" the id value. It works, of course. However now I need to "move" an existing record to a new primary key value (the next available, the value is not so much important, but it must be a new one, and the last one if ordered by id). How can I do it in an "elegant" way? Since the "use NULL at INSERT" does not work too much with UPDATE:
update idtest set id=NULL where id=1;
This simply makes the id of the record zero. I would expect to do the same thing as with INSERT, but it seems my idea was incorrect.
Of course I can use "INSERT ... SELECT" statement, then a DELETE on the old one, or I can use something like MAX(id) + 1 to UPDATE the id of the old record in one step, etc, but I am curious if there is a finer solution.
Also, the MAX(id) solution doesn't seem to work either by the way:
mysql> update idtest set id=max(id)+1 where id=3;
ERROR 1111 (HY000): Invalid use of group function
mysql> update idtest set id=(select max(id)+1 from idtest) where id=3;
ERROR 1093 (HY000): You can't specify target table 'idtest' for update in FROM clause
This is the way I believe:
UPDATE users SET id = (SELECT `AUTO_INCREMENT`
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA = 'test'
AND TABLE_NAME = 'users') WHERE id = 2;
select * from users;
I used by own tables substitute yours.
test is database name, users is table name and id is AUTO_INCREMENT in my case.
EDIT: My Query above works perfect but its side effects are somewhat 'dangerous', upon next insert as AUTO_INCREMENT value will collide with this recently updated record so just next single insert will fail. To avoid that case I've modified above query to a transaction:
START transaction;
UPDATE users SET id = (SELECT `AUTO_INCREMENT`
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA = 'test'
AND TABLE_NAME = 'users') WHERE id = 2;
#renew auto increment to avoid duplicate warning on next insert
INSERT IGNORE INTO users(username) values ('');
COMMIT
Hope this will help someone if not OP.
The way you are trying to update same table is wrong but you can use join on same table
update idtest t
join (select id +1 as id
from idtest order by id desc
limit 1) t1
set t.id=t1.id
where t.id=3;
or
update idtest t
join (select max(id) +1 as id
from idtest ) t1
set t.id=t1.id
where t.id=3;
You can use the REPLACE INTO clause to do the trick.
From the manual:
REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted. See Section 13.2.5, "INSERT Syntax".
EDIT
My mistake (in the comments) that you have to have two unique constraint to achieve this:
When you use the auto_increment value to REPLACE the record, the record will be replaced with the give ID and will not change (however the AI value will increment).
You have to exclude the AI column from the query. You can do that if you have one more UQ constraint.
Check this SQLFiddle demo: http://sqlfiddle.com/#!2/1a702e
The first query will replace all the records (but the id's value will not change).
The second one will replace it too, and the new AI value will be used. (Please note, that the second query does not contain the id column, and there is a UQ constraint on the some column).
You can notice, that the second query uses higher AI values than it is excepted: this is because the first replace incremented the AI value.
If you do not have two unique keys (one for the AI and one for another columns), the REPLACE statement will work as a normal INSERT statement!
(Ofcourse you can change one of the UNIQUE KEYs with a PRIMARY KEY)
This question already has answers here:
Get Updated Value in MySQL instead of affected rows
(5 answers)
Closed 9 years ago.
$query = "UPDATE transaction SET c_status = :status WHERE c_name = :name AND c_id = :id";
$stmt = $this->handle->prepare($query);
$stmt->bindParam(':c_status',$status,PDO::PARAM_STR);
$stmt->bindParam(':c_name',$name,PDO::PARAM_STR);
$stmt->bindParam(':c_id',$id,PDO::PARAM_STR);
return $stmt->execute();
Using the above syntax, I am able to update a record in the transaction table. However, what I only get with the return is a boolean. I want to know if there is a way I can get the transaction_id (the AUTO_INCREMENT field in the transaction table, c_id and c_name where just a column of that) and the rest of its columns?
This question is not related to PDO but to mysql in general.
UPDATE queries are not intended to return anything. To get a row from database you have to use SELECT query.
How can I edit the latest row in the database. I only know it's the last one. I don't know its id.
I don't know which language you are working with, in PHP's mySQL functions you can use
mysql_insert_id()
there are similar function in every other mySQL client library I know of.
Also, there is a native mySQL function!
LAST_INSERT_ID() (with no argument)
returns the first automatically
generated value that was set for an
AUTO_INCREMENT column by the most
recently executed INSERT statement to
affect such a column. For example,
after inserting a row that generates
an AUTO_INCREMENT value, you can get
the value like this:
mysql> SELECT LAST_INSERT_ID();
-> 195
Of course, a primary key with AUTO_INCREMENT is required for these functions to work.
For a table with an auto_increment id field:
UPDATE tbl SET col1 = 'val1' WHERE id = MAX(id);
If it's a row that has been inserted in your script (the same script from which you want to update it) and there is an auto_increment column on your table, you can get that auto_increment value, using functions such as those, for PHP :
mysql_insert_id
mysqli_insert_id
PDO::lastInsertId
There should be an equivalent for probably any language you can possibly be using for your application.
If your are trying to do an update from another script than the one in which you did the insert, and still have an auto_increment column, the best way will probably be to update the row that has the biggest value for that column :
update your_table
set your_column = ...
where id = max(id)
Or, in two steps (not sure it'll work in one) :
select max(id) as id from your_table
update your_table set your_column = ... where id = [what you got with thr first query]
You can also use UPDATE table SET ... WHERE id=LAST_INSERT_ID() (supposing the last insert was on the table you want to query).
I would not use TWO steps to find the last insert ID simply because a new record could be added in the mean time.
Depending on your version, you should be able to call $handle->last_id(); or $handle->{mysql_insertid};
Chris
I am confused about how to copy a column from one table to another table using where. I wrote SQL query but it says transaction lock time exceeded or query returns more than one row.
using mysql
Basically,
I have:
Table 1: Results
BuildID platform_to_insert
Table 2: build
BuildID correct_platform
update results set results.platform_to_insert
= (select correct_platform from
build where results.BuildID = build.BuildID)
I do not believe you need a sub query.
UPDATE results, build
SET results.platform_to_insert = build.correct_platform
WHERE results.BuildID = build.BuildID
There are two options here:
update your tables to use BuildID as a primary key (to avoid duplicates)
update your subquery to only return one result
UPDATE results SET results.platform_to_insert = (
SELECT correct_platform
FROM build
WHERE results.BuildID=build.BuildID LIMIT 1
);