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Anonymous Asked in Cars &Transportation · 2 weeks ago

Does ALTER TABLE change data?

Contents
  1. Can ALTER TABLE change data type?
  2. What happens to data when you ALTER the table structure?
  3. Does ALTER TABLE delete existing data?
  4. How do I edit a table without losing data?
Existing tables can be altered with an ALTER TABLE statement. An ALTER TABLE statement is part of DDL, and is for altering a table schema only; we'll look at .


Can ALTER TABLE change data type?

SQL query to change the column type in PostgreSQL database We can use ALTER TABLE ALTER COLUMN statement to change the datatype of the column. The syntax to change the datatype of the column is the following. In the syntax, Tbl_name: Specify the table name that contains the column that you want to change.

What happens to data when you ALTER the table structure?

It is important to consider how schema changes will affect the data in a table. Adding an extra column to a table will add an extra column to all existing rows, just as it would in a spreadsheet. Deleting a column means all data in that column will be lost forever.

Does ALTER TABLE delete existing data?

No it will not erase your data. It will add a column and all the existing data will be assigned null values in this column.

How do I edit a table without losing data?

There are some good fixes for this issue:1Set a default value (recommended) for the column you're creating.2Create the column without the NOT NULL , set the appropiate values, and then make the column NOT NULL .How to alter MySQL table without losing data? - Stack Overflow

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