I have a table that has several nullable integer columns.  This is undesirable for several reasons, so I am looking to update all nulls to 0 and then set these columns to `NOT NULL`. Aside from changing nulls to `0`, data must be preserved.

I am looking for the *specific SQL syntax* to alter a column (call it `ColumnA`) to &quot;`not null`&quot;.  Assume the data has been updated to not contain nulls.

Using *SQL server 2000*.

Altering a column: null to not null

I would need to rename a few columns in some tables in a SQLite database.
I know that a [similar question][1] has been asked on stackoverflow previously, but it was for SQL in general, and the case of SQLite was not mentioned.

From the SQLite documentation for [ALTER TABLE][2], I gather that it&#39;s not possible to do such a thing &quot;easily&quot; (i.e. a single ALTER TABLE statement).

I was wondering someone knew of a generic SQL way of doing such a thing with SQLite.


  [1]: https://stackoverflow.com/questions/174582/how-do-i-rename-a-column-in-a-database-table-using-sql
  [2]: http://www.sqlite.org/lang_altertable.html

How do I rename a column in a SQLite database table?

I&#39;m pretty new to SQLite 3 and just now I had to add a column to an existing table I had. I went about doing that by doing: `ALTER TABLE thetable ADD COLUMN category;`.

Of course, I forgot to specify that column&#39;s type. The first thing I was thinking about doing was dropping that column and then re-adding it. However, it seems that SQLite does not have a simple way of doing this, and I would have had to backup the table and re-create it without the column.

This seems messy, and I was wondering if there were just a way of modifying/adding a column&#39;s type. I would imagine so, but my searching around yielded no results, being new to SQLite, I imagine it was due to my wording being off in the query.

Modify a Column&#39;s Type in sqlite3

I have created a table and accidentally put `varchar` length as `300` instead of `65353`. How can I fix that?

An example would be appreciated.

How can I modify the size of column in a MySQL table?

I&#39;m adding a new, &quot;NOT NULL&quot; column to my Postgresql database using the following query (sanitized for the Internet):

    ALTER TABLE mytable ADD COLUMN mycolumn character varying(50) NOT NULL;

Each time I run this query, I receive the following error message:

&gt;     ERROR:  column &quot;mycolumn&quot; contains null values

I&#39;m stumped.  Where am I going wrong?

NOTE: I&#39;m using pgAdmin III (1.8.4) primarily, but I received the same error when I ran the SQL from within Terminal.

How can I add a column that doesn&#39;t allow nulls in a Postgresql database?

As the title, I have an existing table which is already populated with 150000 records. I have added an Id column (which is currently null).

I&#39;m assuming I can run a query to fill this column with incremental numbers, and then set as primary key and turn on auto increment. Is this the correct way to proceed? And if so, how do I fill the initial numbers?



SQL Server add auto increment primary key to existing table

I need to modify a column in a SQLite database but I have to do it programatically due to the database already being in production.  From my research I have found that in order to do this I must do the following.

 - Create a new table with new schema
 - Copy data from old table to new table
 - Drop old table
 - Rename new table to old tables name

That seems like a ridiculous amount of work for something that should be relatively easy.  Is there not an easier way? All I need to do is change a constraint on a existing column and give it a default value.



SQLite Modify Column

I am trying to alter column datatype of a primary key to tinyint from int.This column is a foreign key in other tables.So,I get the following error:


----------

&gt; Msg 5074, Level 16, State 1, Line 1 The object &#39;PK_User_tbl&#39; is
&gt; dependent on column &#39;appId&#39;. Msg 5074, Level 16, State 1, Line 1 The
&gt; object &#39;FK_Details_tbl_User_tbl&#39; is dependent on column &#39;appId&#39;. Msg
&gt; 5074, Level 16, State 1, Line 1 The object &#39;FK_Log_tbl_User_tbl&#39; is
&gt; dependent on column &#39;appId&#39;. Msg 4922, Level 16, State 9, Line 1 ALTER
&gt; TABLE ALTER COLUMN appId failed because one or more objects access
&gt; this column.


----------
Is there any other way other than to delete dependencies and recreate them?

ALTER TABLE on dependent column

I’m trying to modify a table to make its primary key column `AUTO_INCREMENT` after the fact.  I have tried the following SQL, but got a syntax error notification.

&lt;!-- language: lang-sql --&gt;

    ALTER TABLE document
    ALTER COLUMN document_id AUTO_INCREMENT

Am I doing something wrong or is this not possible?

&lt;pre&gt;
+--------------------+
| VERSION()          |
+--------------------+
| 5.0.75-0ubuntu10.2 |
+--------------------+
&lt;/pre&gt;

Alter a MySQL column to be AUTO_INCREMENT

I have a table called `provider`. I have three columns called `person`, `place`, `thing`. There can be duplicate persons, duplicate places, and duplicate things, but there can never be a dupicate person-place-thing combination.

How would I ALTER TABLE to add a composite primary key for this table in MySQL with the these three columns?

ALTER TABLE to add a composite primary key

The MySQL reference manual does not provide a clearcut example on how to do this.

I have an ENUM-type column of country names that I need to add more countries to. What is the correct MySQL syntax to achieve this?

Here&#39;s my attempt:

    ALTER TABLE carmake CHANGE country country ENUM(&#39;Sweden&#39;,&#39;Malaysia&#39;);

The error I get is: `ERROR 1265 (01000): Data truncated for column &#39;country&#39; at row 1.`

The `country` column is the ENUM-type column in the above-statement.

&lt;b&gt;SHOW CREATE TABLE&lt;/b&gt; OUTPUT:

    mysql&gt; SHOW CREATE TABLE carmake;
    +---------+---------------------------------------------------------------------+
    | Table   | Create Table
    +---------+---------------------------------------------------------------------+
    | carmake | CREATE TABLE `carmake` (
    `carmake_id` tinyint(4) NOT NULL AUTO_INCREMENT,
    `name` tinytext,
    `country` enum(&#39;Japan&#39;,&#39;USA&#39;,&#39;England&#39;,&#39;Australia&#39;,&#39;Germany&#39;,&#39;France&#39;,&#39;Italy&#39;,&#39;Spain&#39;,&#39;Czech Republic&#39;,&#39;China&#39;,&#39;South Korea&#39;,&#39;India&#39;) DEFAULT NULL,
    PRIMARY KEY (`carmake_id`),
    KEY `name` (`name`(3))
    ) ENGINE=InnoDB AUTO_INCREMENT=49 DEFAULT CHARSET=latin1 |
    +---------+---------------------------------------------------------------------+
    1 row in set (0.00 sec)

&lt;b&gt; SELECT DISTINCT country FROM carmake&lt;/b&gt; OUTPUT:

    +----------------+
    | country        |
    +----------------+
    | Italy          |
    | Germany        |
    | England        |
    | USA            |
    | France         |
    | South Korea    |
    | NULL           |
    | Australia      |
    | Spain          |
    | Czech Republic |
    +----------------+

How do I add more members to my ENUM-type column in MySQL?

I have  a table and one of the columns is &quot;Date&quot; of type datetime. We decided to add a default constraint to that column

    Alter table TableName
    alter column dbo.TableName.Date default getutcdate() 

but this gives me error:

&gt;Incorrect syntax near &#39;.&#39;

Does anyone see anything obviously wrong here, which I am missing (other than having a better name for the column)

Alter column, add default constraint

I have a question about the `ALTER TABLE` command on a really large table (almost 30 millions rows).
One of its columns is a `varchar(255)` and I would like to resize it to a `varchar(40)`.
Basically, I would like to change my column by running the following command:

```sql
ALTER TABLE mytable ALTER COLUMN mycolumn TYPE varchar(40);
```

I have no problem if the process is very long but it seems my table is no more readable during the `ALTER TABLE` command.
Is there a smarter way? Maybe add a new column, copy values from the old column, drop the old column and finally rename the new one?

**Note:** I use PostgreSQL 9.0.

Postgresql - change the size of a varchar column to lower length

In SQL Server, I have a new column on a table:

    ALTER TABLE t_tableName 
        ADD newColumn NOT NULL

This fails because I specify NOT NULL without specifying a default constraint. The table should not have a default constraint.

To get around this, I could create the table with the default constraint and then remove it. 

However, there doesn&#39;t appear to be any way to specify that the default constraint should be named as part of this statement, so my only way to get rid of it is to have a stored procedure which looks it up in the sys.default_constraints table.

This is a bit messy/verbose for an operation which is likely to happen a lot. Does anyone have any better solutions for this?

Can I create a named default constraint in an add column statement in SQL Server?

I have table name called &quot;Person&quot; with following column names 

    P_Id(int),
    LastName(varchar),
    FirstName (varchar).

I forgot to give `NOT NULL` Constraint to `P_Id`.

Now I tried with following query to add `NOT NULL` Constraint to existing column called `P_Id`,

    1. ALTER TABLE  Person MODIFY  (P_Id NOT  NULL);
    2. ALTER TABLE Person ADD CONSTRAINT NOT  NULL NOT NULL (P_Id);

I am getting syntax error....

How to add not null constraint to existing column in MySQL

Entering the following command into a PostgreSQL interactive terminal results in an error:

    ALTER TABLE tbl_name ALTER COLUMN col_name varchar (11);

What is the correct command to alter the data type of a column?


How to alter a column&#39;s data type in a PostgreSQL table?

Is it possible to alter table add MULTIPLE columns in a single statement in sqlite?
The following would not work.
&lt;pre&gt;
alter table test add column mycolumn1 text, add column mycolumn2 text;
&lt;/pre&gt;


sqlite alter table add MULTIPLE columns in a single statement

I have a mySQL table called test:

    create table test(
        locationExpect varchar(120) NOT NULL;
    );


I want to change the locationExpect column to:

    create table test(
        locationExpect varchar(120);
    );

How can it be done quickly?

How to change MySQL column definition?

I&#39;ve tried the following, but I was unsuccessful:

    ALTER TABLE person ALTER COLUMN dob POSITION 37;

How do I alter the position of a column in a PostgreSQL database table?

I am using SQL Server 2008 and Navicat. I need to rename a column in a table using SQL.

    ALTER TABLE table_name RENAME COLUMN old_name to new_name;

This statement doesn&#39;t work.



Rename column SQL Server 2008

I am using the following code to check if the temporary table exists and drop the table if it exists before creating again. It works fine as long as I don&#39;t change the columns. If I add a column later, it will give an error saying &quot;invalid column&quot;. Please let me know what I am doing wrong.

    IF OBJECT_ID(&#39;tempdb..#Results&#39;) IS NOT NULL
        DROP TABLE #Results

    CREATE TABLE #Results
    (
        Company                CHAR(3),
        StepId                TINYINT,
        FieldId                TINYINT,
    )

    select company, stepid, fieldid from #Results

    --Works fine to this point

    IF OBJECT_ID(&#39;tempdb..#Results&#39;) IS NOT NULL
        DROP TABLE #Results

    CREATE TABLE #Results
    (
        Company                CHAR(3),
        StepId                TINYINT,
        FieldId                TINYINT,
        NewColumn            NVARCHAR(50)
    )

    select company, stepid, fieldid, NewColumn from #Results

    --Does not work


Check if a temporary table exists and delete if it exists before creating a temporary table

I have tried:

    ALTER TABLE MY_TABLE 
    ADD STAGE INT NOT NULL;

But it gives this error message:

&gt; ALTER TABLE only allows columns to be added that can contain nulls or
&gt; have a DEFAULT definition specified
           

insert a NOT NULL column to an existing table

I need to create an index on a ~5M rows MySQL table. It is a production table, and I fear a complete block of everything if I run a CREATE INDEX statement... 

Is there a way to create that index without blocking inserts and selects?

Just wondering I have not to stop, create index and restart my system!


Create an index on a huge MySQL production table without table locking

I have been checking the [MySQL Documentation for ALTER TABLE][1] and it does not seem to include a way to add or modify a comment to a column. How can I do this?

    -- for table
    ALTER TABLE myTable COMMENT &#39;Hello World&#39;

    -- for columns
    -- ???

  [1]: http://dev.mysql.com/doc/refman/5.7/en/alter-table.html

Alter MySQL table to add comments on columns

My research and experiments haven&#39;t yielded an answer yet, so I am hoping for some help.

I am modifying the install file of an application which in previous versions did not have a column which I want to add now. I do not want to add the column manually, but in the installation file and only if the new column does not already exist in the table.

The table is created as follows:

    CREATE TABLE IF NOT EXISTS `#__comm_subscribers` (
          `subscriber_id` int(11) NOT NULL auto_increment,
          `user_id` int(11) NOT NULL default &#39;0&#39;,
          `subscriber_name` varchar(64) NOT NULL default &#39;&#39;,
          `subscriber_surname` varchar(64) NOT NULL default &#39;&#39;,
          `subscriber_email` varchar(64) NOT NULL default &#39;&#39;,
          `confirmed` tinyint(1) NOT NULL default &#39;0&#39;,
          `subscribe_date` datetime NOT NULL default &#39;0000-00-00 00:00:00&#39;,
          PRIMARY KEY  (`subscriber_id`),
          UNIQUE KEY `subscriber_email` (`subscriber_email`)
        ) ENGINE=MyISAM CHARACTER SET &#39;utf8&#39; COLLATE &#39;utf8_general_ci&#39; COMMENT=&#39;Subscribers for Comm are stored here.&#39;;

If I add the following, below the create table statement, then I am not sure what happens if the column already exists (and perhaps is populated):

    ALTER TABLE `#__comm_subscribers` ADD `subscriber_surname`;
    ALTER TABLE `#__comm_subscribers` MODIFY `subscriber_surname` varchar(64) NOT NULL default &#39;&#39;;

So, I tried the following which I found somewhere. This does not seem to work but I am not entirely sure I used it properly.

    /*delimiter &#39;//&#39;
    CREATE PROCEDURE addcol() BEGIN
    IF NOT EXISTS(
	SELECT * FROM information_schema.COLUMNS
	WHERE COLUMN_NAME=&#39;subscriber_surname&#39; AND TABLE_NAME=&#39;#__comm_subscribers&#39;
	)
	THEN
		ALTER TABLE `#__comm_subscribers`
		ADD COLUMN `subscriber_surname` varchar(64) NOT NULL default &#39;&#39;;
    END IF;
    END;
    //
    delimiter &#39;;&#39;
    CALL addcol();
    DROP PROCEDURE addcol;*/

Does anyone have a good way to do this?


add column to mysql table if it does not exist

When doing an ALTER TABLE statement in MySQL, the whole table is read-locked (allowing concurrent reads, but prohibiting concurrent writes) for the duration of the statement. If it&#39;s a big table, INSERT or UPDATE statements could be blocked for a looooong time. Is there a way to do a &quot;hot alter&quot;, like adding a column in such a way that the table is still updatable throughout the process?

Mostly I&#39;m interested in a solution for MySQL but I&#39;d be interested in other RDBMS if MySQL can&#39;t do it.

To clarify, my purpose is simply to avoid downtime when a new feature that requires an extra table column is pushed to production. Any database schema *will* change over time, that&#39;s just a fact of life. I don&#39;t see why we should accept that these changes must inevitably result in downtime; that&#39;s just weak.

ALTER TABLE without locking the table?

We&#39;ve recently had the need to add columns to a few of our existing SQLite database tables.  This can be done with [`ALTER TABLE ADD COLUMN`][1].  Of course, if the table has already been altered, we want to leave it alone.  Unfortunately, SQLite doesn&#39;t support an `IF NOT EXISTS` clause on `ALTER TABLE`.

Our current workaround is to execute the ALTER TABLE statement and ignore any &quot;duplicate column name&quot; errors, just like [this Python example][2] (but in C++).

However, our usual approach to setting up database schemas is to have a .sql script containing `CREATE TABLE IF NOT EXISTS` and `CREATE INDEX IF NOT EXISTS` statements, which can be executed using `sqlite3_exec` or the `sqlite3` command-line tool.  We can&#39;t put `ALTER TABLE` in these script files because if that statement fails, anything after it won&#39;t be executed.

I want to have the table definitions in one place and not split between .sql and .cpp files.  Is there a way to write a workaround to `ALTER TABLE ADD COLUMN IF NOT EXISTS` in pure SQLite SQL?


  [1]: http://www.sqlite.org/lang_altertable.html
  [2]: https://stackoverflow.com/questions/2354696/alter-table-sqlite-how-to-check-if-a-column-exists-before-alter-the-table/2354829#2354829

ALTER TABLE ADD COLUMN IF NOT EXISTS in SQLite

I need to change the primary key of a table to an identity column, and there&#39;s already a number of rows in table. 

I&#39;ve got a script to clean up the IDs to ensure they&#39;re sequential starting at 1, works fine on my test database. 

What&#39;s the SQL command to alter the column to have an identity property?

Adding an identity to an existing column

Given the table created using: 

    CREATE TABLE tbl_Country
    (
      CountryId INT NOT NULL AUTO_INCREMENT,
      IsDeleted bit,
      PRIMARY KEY (CountryId) 
    )

How can I delete the column `IsDeleted `?

How to delete a column from a table in MySQL

I have the following set up,

    CREATE TABLE auth_user ( id int PRIMARY KEY );
    CREATE TABLE links_chatpicmessage ();

I&#39;m trying to **add a column** named `sender` to `links_chatpicmessage` which is a foreign key to another table called `auth_user`&#39;s `id` column.

To achieve the above, I&#39;m trying the following on terminal:

    ALTER TABLE links_chatpicmessage
      ADD FOREIGN KEY (sender)
      REFERENCES auth_user;

But this gives me an error: 

&gt; ERROR:  column &quot;sender&quot; referenced in foreign key constraint does not
&gt; exist

How do I fix this?

Adding a column as a foreign key gives ERROR column referenced in foreign key constraint does not exist

I need to add multiple columns to a table but position the columns **after** a column called `lastname`.

I have tried this:

    ALTER TABLE `users` ADD COLUMN
    (
        `count` smallint(6) NOT NULL,
        `log` varchar(12) NOT NULL,
        `status` int(10) unsigned NOT NULL
    ) 
    AFTER `lastname`;

I get this error:

&gt; You have an error in your SQL syntax; check the manual that
&gt; corresponds to your MySQL server version for the right syntax to use
&gt; near &#39;) AFTER `lastname`&#39; at line 7

&lt;br&gt;
How can I use AFTER in a query like this?

Adding multiple columns AFTER a specific column in MySQL

How do I rename a column in table `xyz`? The columns are:

    Manufacurerid, name, status, AI, PK, int

I want to rename to `manufacturerid`

I tried using PHPMyAdmin panel, but I get this error:

    MySQL said: Documentation
    #1025 - Error on rename of &#39;.\shopping\#sql-c98_26&#39; to &#39;.\shopping\tblmanufacturer&#39; (errno: 150)

 





Error renaming a column in MySQL

I have this code:

    ALTER TABLE `settings`
    ADD COLUMN `multi_user` TINYINT(1) NOT NULL DEFAULT 1

And I want to alter this table only if this column doesn&#39;t exist.

I&#39;m trying a lot of different ways, but nothing works:

    ALTER TABLE `settings`
    ADD COLUMN IF NOT EXISTS `multi_user` TINYINT(1) NOT NULL DEFAULT 1

With procedure:

    DELIMITER $$
    CREATE PROCEDURE Alter_Table()
    BEGIN
        DECLARE _count INT;
        SET _count = (  SELECT COUNT(*) 
                        FROM INFORMATION_SCHEMA.COLUMNS
                        WHERE   TABLE_NAME = &#39;settings&#39; AND 
                                COLUMN_NAME = &#39;multi_user&#39;);
        IF _count = 0 THEN
            ALTER TABLE `settings` ADD COLUMN `multi_user` TINYINT(1) NOT NULL DEFAULT 1
        END IF;
    END $$
    DELIMITER ; 

I got error in END IF, then in END and then in 1

How can I make this as simple as possible?

MySQL: ALTER TABLE if column not exists

I created a table in MySQL with on column `itemID`. 

After creating the table, now I want to change this column to `AUTOINCREMENT`. 

**How can this be done using ALTER statements**? 

Table definition: 

`ALLITEMS (itemid int(10) unsigned, itemname varchar(50))`

I am using the following code but it is throwing a syntax error

**Error: syntax incorrect**.

    ALTER TABLE allitems
    MODIFY itemid INT(10) UNSIGNED AUTOINCREMENT; 

ALTER table - adding AUTOINCREMENT in MySQL

I came across an old table today with a datetime column called &#39;Created&#39; which allows nulls.  Now, I&#39;d want to change this so that it is NOT NULL, and also include a constraint to add in a default value (getdate()).

So far I&#39;ve got the following script, which works fine provided that i&#39;ve cleaned up all the nulls beforehand:

    ALTER TABLE dbo.MyTable ALTER COLUMN Created DATETIME NOT NULL 

Is there any way to also specify the default value as well on the ALTER statement?

Change a Nullable column to NOT NULL with Default Value

The `SQL` query that I have used is :

    ALTER TABLE oldtable RENAME TO newtable;

But, it gives me an error.

&gt; Server: Msg 156, Level 15, State 1, Line 1  
&gt; Incorrect syntax near the keyword &#39;TO&#39;.


How to rename a table in SQL Server?

I am creating a script that will be run in a MS SQL server. This script will run multiple statements and needs to be transactional, if one of the statement fails the overall execution is stopped and any changes are rolled back.

I am having trouble creating this transactional model when issuing ALTER TABLE statements to add columns to a table and then updating the newly added column. In order to access the newly added column right away, I use a GO command to execute the ALTER TABLE statement, and then call my UPDATE statement. The problem I am facing is that I cannot issue a GO command inside an IF statement. The IF statement is important within my transactional model. This is a sample code of the script I am trying to run. Also notice that issuing a  GO command, will discard the @errorCode variable, and will need to be declared down in the code before being used (This is not in the code below).

    BEGIN TRANSACTION
    
    DECLARE @errorCode INT
    SET @errorCode = @@ERROR
    
    -- **********************************
    -- * Settings
    -- **********************************
    IF @errorCode = 0
    BEGIN
     BEGIN TRY
      ALTER TABLE Color ADD [CodeID] [uniqueidentifier] NOT NULL DEFAULT (&#39;{00000000-0000-0000-0000-000000000000}&#39;)
      GO
     END TRY
     BEGIN CATCH
      SET @errorCode = @@ERROR
     END CATCH
    END
    
    IF @errorCode = 0
    BEGIN
     BEGIN TRY
      UPDATE Color
      SET CodeID= &#39;B6D266DC-B305-4153-A7AB-9109962255FC&#39;
      WHERE [Name] = &#39;Red&#39;
     END TRY
     BEGIN CATCH
      SET @errorCode = @@ERROR
     END CATCH
    END
    
    -- **********************************
    -- * Check @errorCode to issue a COMMIT or a ROLLBACK
    -- **********************************
    IF @errorCode = 0
    BEGIN
     COMMIT
     PRINT &#39;Success&#39;
    END
    ELSE 
    BEGIN
     ROLLBACK
     PRINT &#39;Failure&#39;
    END

So what I would like to know is how to go around this problem, issuing ALTER TABLE statements to add a column and then updating that column, all within a script executing as a transactional unit.

Add column to table and then update it inside transaction

I am trying to change a column from a `varchar(50)` to a `nvarchar(200)`. What is the SQL command to alter this table? 

How do you change the datatype of a column in SQL Server?

For example:

    ALTER TABLE webstore.Store MODIFY COLUMN (
      ShortName VARCHAR(100),
      UrlShort VARCHAR(100)
    );

The above however does not work. I am using MySql 5.x

How do I Alter Table Column datatype on more than 1 column?

I want to script a table as Alter to a New Query Editor Window. But this option is disabled. How can I do this?

Right click script alter table disabled in SQL Server Management Studio

I wrongly named a column `hased_password` instead of `hashed_password`.

How do I update the database schema, using migration to rename this column?


How can I rename a database column in a Ruby on Rails migration?

I am using a query to alter the charset of a column


    ALTER TABLE `media_value_report` 
        CHANGE `index_page_body` `index_page_body` TEXT CHARACTER  
        SET utf8 NULL DEFAULT NULL

i want to do this for other columns  main_title, landing_page_body as well. But am getting a #1064 error while executing. Can i alter-change multiple columns in  a single query?

I tried but i found in goog search that is not possible to alter in a single query. 



Alter multiple columns in a single statement

MySQL very slow for alter table query

How to change the column size of the `salary` column in the `employee` table from `numeric(18,0)` to `numeric(22,5)`



Altering column size in SQL Server

I created the table Test_Project2 in Oracle SQL Developer. After that I realized that the column proj_name is of a small size, so I decided to modify the column using the follwoing statement

	ALTER TABLE TEST_PROJECT2 MODIFY proj_name VARCHAR2(300);
	
but for some reason Oracle SQL Developer underscores the semi-colon with red and I do not what is mistake and how to correct it

**Test_Project2**:

	CREATE TABLE Test_Project2 (
	proj_id number(30),
	proj_name VARCHAR2 (30),
	proj_desc VARCHAR2(300)
	);

how to modify the size of a column

I know, we can not rename a column using `modify column syntax`,but can `change column syntax`.

My question is: what is the main usage of `modify syntax`?

For example,&lt;br /&gt;

    alter table tablename change col1 col1 int(10) not null
instead of 

    alter table tablename modify col1 int(10) not null

&lt;br /&gt;
&lt;br /&gt;
**Edited**&lt;br /&gt;
Question replaced&lt;br /&gt;

What is the main usage of `modify syntax`?

Above question was replaced by below

Why we have to use change column instead of modify column?

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