May 2020
Beginner
564 pages
14h 9m
English
Content preview from Learn SQL Database Programming
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Changing the data type of a column
Let's say you discover that you need the schoolID values to be 16 characters long instead of 15 characters long. You can update the length of the field by executing the following query:
USE foraltering;ALTER TABLE tableforalteringCHANGE COLUMN schoolID schoolID VARCHAR(16);
You will need to specify the same column name twice. This is because you can rename the column at the same time as changing the data type, but since you aren't changing the column name, MySQL requires you to place the column name in the query twice as part of the CHANGE COLUMN statement.
If you realize that you want the schoolID values to be 7 characters long, you can execute the following query to change the length of the field:
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