I have an auto increment column ID, and for some situation I wanted the other column to be equal to the primary key + 1 value
ID | other
1 | 2
2 | 3
3 | 4
4 | 123 (some situation, it is not always plus 1)
How can I achieve this?
Here's what I have tried
INSERT INTO table (`ID`,`other`) VALUES ('',(SELECT MAX(ID)+1 FROM table))
But that returns an error
You can't specify target table 'table' for update in FROM clause
Try Below query:
ALTER TABLE dbo.table ADD
Column AS ([ID]+1)
GO
It will definitely work
Using a normal AUTO_INCREMENT column as id, I cannot think of a way to do this in MySQL. Triggers, which otherwise would have been an option, don't work well with AUTO_INCREMENT columns.
The only way I see is to do two commands for an INSERT;
INSERT INTO bop (value) VALUES ('These values should be 1 and 2');
UPDATE bop SET other = id+1 WHERE id = LAST_INSERT_ID();
An SQLfiddle to test with.
The closest I'm getting to what you're looking for is to generate sequences separately from AUTO_INCREMENT using a function, and use that instead to generate the table id;
DELIMITER //
CREATE TABLE bop (
id INT UNIQUE,
other INT,
value VARCHAR(64)
)//
CREATE TABLE bop_seq ( seq INT ) // -- Sequence table
INSERT INTO bop_seq VALUES (1) // -- Start value
CREATE FUNCTION bop_nextval() RETURNS int
BEGIN
SET #tmp = (SELECT seq FROM bop_seq FOR UPDATE);
UPDATE bop_seq SET seq = seq + 1;
RETURN #tmp;
END//
CREATE TRIGGER bop_auto BEFORE INSERT ON bop
FOR EACH ROW
SET NEW.id = bop_nextval(), NEW.other=NEW.id + 1;
//
That'd let you do inserts and have it autonumber like you want. The FOR UPDATE should keep the sequence transaction safe, but I've not load tested so you may want to do that.
Another SQLfiddle.
I solved this by updating 2 times the DB..
I wanted to do +1 from 19 till ..
UPDATE `table` SET `id`=`id`+101 WHERE id <= 19
UPDATE `table` SET `id`=`id`-100 WHERE id <= 119 AND id >= 101
Related
I have a table in MYSQL database with two fields:
Id (auto increment field).
Post_Id.
When I insert a new record both fields should have the same value. So I should update post_id with Id value, and at the same time make sure that I update the field with the right value not with any other new inserted record value.
I tried this SQL statement but it was very slow and I was not sure that I select the right value:
set #auto_id := (SELECT AUTO_INCREMENT
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME='table_name'
AND TABLE_SCHEMA=DATABASE() );
update table_name set post_id= #auto_id where id=#auto_id ;
I don't have long experience with MySQL and I cannot change the table structure .
The approach you followed is not transaction safe as well.
The best option I can think about is to use trigger
Edit: According to #lagripe's mentionings
CREATE TRIGGER sometrigger
AFTER INSERT ON sometable
BEGIN
SET NEW.post_id := (SELECT id from sometable order by DESC limit 1) + 1 ; // you may need +1 here. I couldn't test it.
END
or you may consider to use LAST_INSERT_ID
insert into table_name values ( .... );
update table_name set post_id = LAST_INSERT_ID();
but why do you need two columns with the same id at first place?
if you really need why don't you use computed/generated columns?
CREATE TABLE Table1(
id DOUBLE,
post_id DOUBLE as (id)
);
you can use triggers :
CREATE TRIGGER UpdatePOST_id
BEFORE INSERT ON table_db
FOR EACH ROW
SET NEW.post_id := (select id from table_db order by id DESC LIMIT 1)+1 ;
from now on, whatever you insert your as a value in post_id column will be replaced with the id inserted automatically.
Test :
|id|post_id|
|20| 20 |
|21| 21 |
|22| 22 |
|23| 23 |
To drop the trigger :
DROP trigger UpdatePOST_id
How to assign unique auto incrementing values to a certain column? Kind of like AUTO_INCREMENT does but it should be NULL at the time of insertion and assigned at some later point.
I have a table that gets regular data inserts and a few workers that process that data and set processed_at datetime field when they're done. Now I want incrementally select new processed rows since the last call. If I naively use where processed_at > #last_update_time I'm afraid there might be a situation where some records are processed at the same second and I miss some rows.
update: Can I just do
begin;
select #max := max(foo) from table1;
update table1 set foo = #max + 1 where id = 'bar' limit 1;
commit;
if foo column is indexed?
You can use a trigger to implement that.
CREATE TABLE my_increment (value INT, table_name TEXT);
INSERT INTO my_increment VALUES (0, 'your_table_name');
CREATE TRIGGER pk AFTER UPDATE ON your_table_name
BEGIN
UPDATE my_increment
SET value = value + 1
WHERE table_name = 'your_table_name';
UPDATE your_table_name
SET ID2 = (
SELECT value
FROM my_increment
WHERE table_name = 'your_table_name')
WHERE ROWID = new.ROWID;
END;
But bear in mind that this trigger will work on every execution of the Update query.
You can also do it manually:
Create the table to store increment value:
CREATE TABLE my_increment (value INT, table_name TEXT);
INSERT INTO my_increment VALUES (0, 'your_table_name');
Then when you want to update the table, get the last value from this table and insert value+1 to your column needed to be incremented.
I have fields in the table which are id, name, employee_id. The id column is the primary key with auto increment.In this table,
I need one column which called employee_id start from A5001, A5002, A5003...and soon.
I tried below code.
Table
CREATE TABLE table1_seq
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
);
CREATE TABLE table1
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30),
employee_id VARCHAR(30) NOT NULL DEFAULT '0'
);
Now the trigger
DELIMITER $$
CREATE TRIGGER tg_table1_insert
BEFORE INSERT ON table1
FOR EACH ROW
BEGIN
INSERT INTO table1_seq VALUES (NULL);
SET NEW.employee_id = CONCAT('A', LPAD(LAST_INSERT_ID(), 4, '500'));
END$$
DELIMITER ;
Then just insert rows to table1
INSERT INTO Table1 (name)
VALUES ('ABC'),('ZXD'),('POI');
Finally, I got my output.
1|ABC | A5001
2|ZXD | A5002
3|POI | A5003
and so on
Now My issue is, I inserted 1000 rows in the table so my id is 1000 but there is some issue with my employee_id because after getting the A5999 it starts from A1000 which is totally wrong I need continuously like A6000, A6001, A6002.. and so on
I think there is some issue with my trigger.
Would you help me out in this?
You can use mathematical addition instead of string padding:
SET NEW.employee_id = CONCAT('V', 5000 + LAST_INSERT_ID());
Explanation:
I'm just adding 5000 to last insert ID. Think of it:
1st ID would be 5000 + 1 = 5001
999th ID would be 5000 + 999 = 5999
1000th ID would be 5000 + 1000 = 6000
It will never throw an ID shorter than 4 digits, so there is no need of LPAD.
Warning: You have to think what do you want after 4999th insert. It will cause an ID of 5 digits (5000 + 5000 = 10000). If you don't have a problem with 5 digits, leave it this way.
I have a table someTable with a column bin of type VARCHAR(4). Whenever I insert to this table, bin should be a unique combination of characters and numbers. Unique in this sense meaning has not appeared before in the table in another row.
bin is in the form of AA00, where A is a character A-F and 0 is a number 0-9.
Say I insert to this table once: it should come up with a bin value which doesn't appear before. Assuming the table was empty, the first bin could be AA11. On second insertion, it should be AA12, and then AA13, etc.
AA00, AA01, ... AA09, AA10, AA11, ... AA99, AB00, AB01, ... AF99, BA00, BA01, ... FF99
It doesn't matter this table can contain only 3,600 possible rows. How do I create this code, specifically finding a bin that doesn't already exist in someTable? It can be in order as I've described or a random bin, as long as it doesn't appear twice.
CREATE TABLE someTable (
bin VARCHAR(4),
someText VARCHAR(32),
PRIMARY KEY(bin)
);
INSERT INTO someTable
VALUES('?', 'a');
INSERT INTO someTable
VALUES('?', 'b');
INSERT INTO someTable
VALUES('?', 'c');
INSERT INTO someTable
VALUES('?', 'd');
Alternatively, I can use the below procedure to insert instead:
CREATE PROCEDURE insert_someTable(tsomeText VARCHAR(32))
BEGIN
DECLARE var (VARCHAR(4) DEFAULT (
-- some code to find unique bin
);
INSERT INTO someTable
VALUES(var, tsomeText);
END
A possible outcome is:
+------+----------+
| bin | someText |
+------+----------+
| AB31 | a |
| FC10 | b |
| BB22 | c |
| AF92 | d |
+------+----------+
As Gordon said, you will have to use a trigger because it is too complex to do as a simple formula in a default. Should be fairly simple, you just get the last value (order by descending, limit 1) and increment it. Writing the incrementor will be somewhat complicated because of the alpha characters. It would be much easier in an application language, but then you run into issues of table locking and the possibility of two users creating the same value.
A better method would be to use a normal auto-increment primary key and translate it to your binary value. Consider your bin value as two base 6 characters followed by two base 10 values. You then take the id generated by MySQL which is guaranteed to be unique and convert to your special number system. Calculate the bin and store it in the bin column.
To calculate the bin:
Step one would be to get the lower 100 value of the decimal number (mod 100) - that gives you the last two digits. Convert to varchar with a leading zero.
Subtract that from the id, and divide by 100 to get the value for the first two digits.
Get the mod 6 value to determine the 3rd (from the right) digit. Convert to A-F by index.
Subtract this from what's left of the ID, and divide by 6 to get the 4th (from the right) digit. Convert to A-F by index.
Concat the three results together to form the value for the bin.
You may need to edit the following to match your table name and column names, but it should so what you are asking. One possible improvement would be to have it cancel any inserts past the 3600 limit. If you insert the 3600th record, it will duplicate previous bin values. Also, it won't insert AA00 (id=1 = 'AA01'), so it's not perfect. Lastly, you could put a unique index on bin, and that would prevent duplicates.
DELIMITER $$
CREATE TRIGGER `fix_bin`
BEFORE INSERT ON `so_temp`
FOR EACH ROW
BEGIN
DECLARE next_id INT;
SET next_id = (SELECT AUTO_INCREMENT FROM information_schema.TABLES WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME='so_temp');
SET #id = next_id;
SET #Part1 = MOD(#id,100);
SET #Temp1 = FLOOR((#id - #Part1) / 100);
SET #Part2 = MOD(#Temp1,6);
SET #Temp2 = FLOOR((#Temp1 - #Part2) / 6);
SET #Part3 = MOD(#Temp2,6);
SET #DIGIT12 = RIGHT(CONCAT("00",#Part1),2);
SET #DIGIT3 = SUBSTR("ABCDEF",#Part2 + 1,1);
SET #DIGIT4 = SUBSTR("ABCDEF",#Part3 + 1,1);
SET NEW.`bin` = CONCAT(#DIGIT4,#DIGIT3,#DIGIT12);
END;
$$
DELIMITER ;
I'm trying to insert a data as a primary ID that has one alphanumerical value and two numerical value in MySQL database. This data will auto incrementally generate number, but the alphanumerical value will be fixed. Like, D1, D2....D54, D55, D56 etc. Here, 'D' is always the same, but the number will be automatically incremented. Is there any way to do this?
First of all it's unadvisable to do so, like others commented, you can have this id value generated on the fly.
But if nonetheless you want it your way there're at least two ways to do so:
More or less reliable way involves using a separate table for sequencing and a trigger
Schema:
CREATE TABLE Table1_seq
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY
);
CREATE TABLE Table1
(
`id` VARCHAR(10) NOT NULL PRIMARY KEY DEFAULT '',
...
);
Trigger:
DELIMITER $$
CREATE TRIGGER tg_bi_table1
BEFORE INSERT ON table1
FOR EACH ROW
BEGIN
INSERT INTO table1_seq() VALUES();
SET NEW.id = CONCAT('D', LPAD(LAST_INSERT_ID(), 4,'0'));
END$$
DELIMITER ;
Then you just insert your rows to table1
INSERT INTO Table1 () VALUES (),(),();
And you'll get
| ID |
---------
| D0001 |
| D0002 |
| D0003 |
Here is SQLFiddle demo
Unreliable way is to generate your new id on the fly in INSERT statement itself
INSERT INTO Table1 (id, ...)
SELECT CONCAT('D', LPAD(COALESCE(SUBSTR(MAX(id), 2), 0) + 1, 4, '0')),
...
FROM table1
Here is SQLFiddle demo
The problems with this approach:
Under heavy load two concurrent sessions can grab the same MAX(id) value and therefore generate the same new id leading to the failure of insert.
You can't use multi-insert statements
We can't set auto-increment for alphanumeric. In your case if D is always same then no need to add it to your pk field. Keep your constant in a separate field and add it when you select.