how to ensure mysql column has 4 character ?
Due to using the MATCH function with minimum 4 char, i want my primary key which is a INT to be at least 4 char.
How can i do it ?
eg. 1 will be 0001 in sql table
Use ZEROFILL attribute of column. Alter your Primary key column to have zerofill enabled.
Try this:
ALTER TABLE `tablename` CHANGE
COLUMN `id` `id` INT(4) ZEROFILL NOT NULL AUTO_INCREMENT ;
You can use MySQL's LPAD function:
SELECT LPAD('1',4,'0');
-> '0001'
Docs here.
Assuming your primary key is an auto-incremented id.
Temporarily take the auto-increment off.
Add 999 to every id. (Of course if other tables use this id as a foreign key, you are going to have to adjust them, too).
Re-add the auto-increment, but make sure that it starts at at least 1000. See: How to set initial value and auto increment in MySQL?
Related
I need that the values for a ColumnID, which is a Primary Key, to start at 100 and increment by 5. This condition is asked to be included as a constraint before populating the tables. I already created the tables, I just need to add that constraint. I know I can't use AUTO_INCREMENT because the increase is only by 1. Is there a way to do it in MySQL?
MySQL does not provide any built-in function to create a sequence for a table's rows or columns. But we can generate it via SQL query.
Example:
Let us understand it with the help of the following example. First, we need to create a new table and make sure that there is one column with the AUTO_INCREMENT attribute and that too, as PRIMARY KEY.
Execute the below query to create a table:
CREATE TABLE Insects (
Id INT AUTO_INCREMENT PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
Type VARCHAR(30) NOT NULL,
Origin VARCHAR(30) NOT NULL
);
Then you can alter your column to start from another value:
ALTER TABLE Insects AUTO_INCREMENT=100;
You can check it here.
Scenario is that I have 2 tables of the same structure, however I only want to allow php permissions to update table B, while table A can only be updated via DBMS.
These 2 tables are merged into a single php array, so I would like to set primary key ranges to seperate them at this point to avoid conflict of primary key (a simple autoincrement integer for best indexing).
As far as I know the simplest would be to constrain table A to have primary key auto increment values from 1000000 to 1999999 and then table B 2000000 upwards.
Is this possible to constrain min-max autoincrement values (I know I can start them at a given integer so asking if there is a simple 'max' to put on table A).
This simple configuration would ensure integrity.
Would an 'after_insert' type trigger work to remove the new row and throw an SQL error ?
You could create one table with id as mediumint (max 8 388 607 or twice as much for unsigned):
create table tableA( id mediumint(5) not null auto_increment, `test` varchar(5), primary key (id)) ;
and second with int and auto_increment value set over mediumint max:
create table tableB( id int(5) not null auto_increment, `test` varchar(5), primary key (id)) auto_increment=8388608 ;
https://dev.mysql.com/doc/refman/8.0/en/integer-types.html
But i think that much more elegant would be to utilize auto_increment_increment mechanism.
auto-increment-increment = 2 //global for all tables in mysql.ini
SET ##auto_increment_increment=2; //run-time just for one session
Set in tableA first auto_increment=1 and in tableB auto_increment=2 and You will never collide. One table will have odd ids and second will have even ids. This way You do not have to worry about reaching id limit.
So, I am looking for a way to sequence the rows of my athena table. I have already tried:
ROW_NUMBER() OVER ()
But then this leads to Query exhausted resources at this scale factor error. It has to be a unique value for every row, so yes it doesn't need to be an integer. The method should be performance effective if it can be.
Please provide SHOW CREATE TABLE for the table in question.
If you don't already have an AUTO_INCREMENT column on the table, consider the following.
ALTER TABLE t
ADD COLUMN id INT UNSIGNED AUTO_INCREMENT NOT NULL,
ADD INDEX(id);
If you don't already have a PRIMARY KEY on the table, do this instead:
ALTER TABLE t
ADD COLUMN id INT UNSIGNED AUTO_INCREMENT NOT NULL,
ADD PRIMARY KEY(id);
You can give each row a unique id, uuid, using the uuid() function. Here are the docs:
https://trino.io/docs/current/functions/uuid.html
I have come across two ways to increment the ids in mysql automatically.
One is SERIAL and other is AUTOINCREMENT.
So Suppose i want to create a table myfriends.
I can create it in two ways like:
1)
mysql> create table myfriends(id int primary key auto_increment,frnd_name varchar(50) not null);
2)
mysql> create table myfriends(id serial primary key,frnd_name varchar(50) not null);
What is difference between the two ?
OR
Do anyone way has advantages over other ?
Please Help.
As per the docs
SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.
So, be careful when creating a reference to a SERIAL PK, since that reference column has to be of this exact type.
AUTO_INCREMENT is an attribute of a specific column of any numeric type (int or float), both signed and unsigned. When rows are inserted it automatically assigns sequential numbers, so you don't have to (e.g. by using LAST_INSERT_ID()). See http://dev.mysql.com/doc/refman/5.0/en/example-auto-increment.html
SERIAL is an alias that combines column type casting (BIGINT specifically), AUTO_INCREMENT, UNSIGNED and other attributes for a specific column (see quote from docs below). See https://dev.mysql.com/doc/refman/8.0/en/numeric-type-syntax.html
SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.
SERIAL DEFAULT VALUE in the definition of an integer column is an alias for NOT NULL AUTO_INCREMENT UNIQUE.
From mysql doc
SERIAL is an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE.
SERIAL DEFAULT VALUE in the definition of an integer column is an
alias for NOT NULL AUTO_INCREMENT UNIQUE.
If no value is specified for the AUTO_INCREMENT column, MySQL assigned sequence numbers automatically. You can also explicitly assign NULL or 0 to the column to generate sequence numbers. MySQL doesn't automatically decrease the autoincrement value when you delete a row. Reasons are:
Danger of broken data integrity (imagine multiple users perform
deletes or inserts...doubled entries may occur or worse)
Errors may occur when you use master slave replication or
transactions
I am entering records in the MySQL DB. Now I want to have a "Serial_Number" field that increements automatically whenever a record is entered into the DB.
I don't want this "Serial_Number" field to be the primary key of the DB.
How can I create this field (with the attributes needed to be set).
I am using "SQL YOG" to access MySQL. If you are aware of the SQL YOG then tell me how to do that through SQL YOG.
The AUTO_INCREMENT column has to have a UNIQUE KEY constraint associated to it.
For instance, this will work just fine:
CREATE TABLE AutoNotId
(
Id INTEGER PRIMARY KEY,
Auto INTEGER AUTO_INCREMENT,
UNIQUE (Auto)
);
Edit:
The ALTER statement would look somewhat like this:
ALTER TABLE AutoNotId
MODIFY COLUMN Auto INTEGER AUTO_INCREMENT,
ADD UNIQUE (Auto);
I recommended, however the use of the long-hand syntax to specify the name of the UNIQUE constraint; But you can always refer to MySQL's Reference Manual for the exact specifications.
In MySQL tables can only have one auto increment field and they must be indexed.
There can be only one AUTO_INCREMENT column per table, it must be indexed, and it cannot have a DEFAULT value.
Is there a reason you don't want it to be the primary key?
If you want an incrementing value, you could fudge it by running updates after each insert:
SELECT MAX(serial) + 1 FROM myTable;
UPDATE myTable SET serial = <that number> WHERE id = ...
I don't think you can have an auto increment field:
CREATE TABLE `t` (`dd` int(11) NOT NULL)
ALTER TABLE `t` CHANGE `dd` `dd` INT( 11 ) NOT NULL AUTO_INCREMENT
MySQL said: Documentation
#1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key
You cannot do this in MySQL. From the doc:
There can be only one AUTO_INCREMENT
column per table, it must be indexed,
and it cannot have a DEFAULT value. An
AUTO_INCREMENT column works properly
only if it contains only positive
values. Inserting a negative number is
regarded as inserting a very large
positive number. This is done to avoid
precision problems when numbers “wrap”
over from positive to negative and
also to ensure that you do not
accidentally get an AUTO_INCREMENT
column that contains 0.
For MyISAM and BDB tables, you can
specify an AUTO_INCREMENT secondary
column in a multiple-column key. See
Section 3.6.9, “Using AUTO_INCREMENT”.
create table mytable (
ID INT IDENTITY(1,1) PRIMARY KEY,
SN INT IDENTITY(1,1)
)