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You can modify the data type of a column in SQL Server by using SQL Server Management Studio or Transact-SQL. Modifying the data type of a column that already contains data can result in the permanent loss of data when the existing data is converted to the new type.
The syntax to modify a column in a table in PostgreSQL (using the ALTER TABLE statement) is: ALTER TABLE table_name ALTER COLUMN column_name TYPE column_definition; table_name. The name of the table to modify.
How to increase the length of a character varying datatype in Postgres without data loss. Run the following command: alter table TABLE_NAME alter column COLUMN_NAME type character varying(120); This will extend the character varying column field size to 120.
First, specify the name of the table that you want to update data after the UPDATE keyword. Second, specify columns and their new values after SET keyword. The columns that do not appear in the SET clause retain their original values. Third, determine which rows to update in the condition of the WHERE clause.
See documentation here: http://www.postgresql.org/docs/current/interactive/sql-altertable.html
ALTER TABLE tbl_name ALTER COLUMN col_name TYPE varchar (11);
If data already exists in the column you should do:
ALTER TABLE tbl_name ALTER COLUMN col_name TYPE integer USING col_name::integer;
As pointed out by @nobu and @jonathan-porter in the comments to @derek-kromm's answer, somewhat cryptically.
Cool @derek-kromm, Your answer is accepted and correct, But I am wondering if we need to alter more than the column. Here is how we can do.
ALTER TABLE tbl_name
ALTER COLUMN col_name TYPE varchar (11),
ALTER COLUMN col_name2 TYPE varchar (11),
ALTER COLUMN col_name3 TYPE varchar (11);
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