What is the default value in MySQL?

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In MySQL, the default value refers to the value that is automatically assigned to a column if no specific value is provided during the insertion of a new row into a table. It is the value that MySQL assumes when there is no explicit value given.

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Table of Contents

What is the default value in MySQL?

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The default value in MySQL is the value that is automatically assigned to a column if no specific value is provided during the insertion of a new row into a table.

What is the purpose of default values in MySQL?

The main purpose of default values in MySQL is to ensure that every row has a valid value for a specific column, even if no explicit value is provided. This helps in maintaining data integrity and consistency.

How are default values defined in MySQL?

Default values in MySQL can be defined during table creation using the DEFAULT keyword followed by the desired value, or they can be altered later using the ALTER TABLE statement.

Can default values be specified for all data types in MySQL?

Yes, default values can be specified for almost all data types in MySQL, including numeric, string, date, and even Boolean types.

What happens if a column has no default value, and no value is provided during insertion?

If a column has no default value defined, and no value is provided during insertion, the column will either be assigned a null value (if allowed) or MySQL will apply its default behavior for that particular data type.

Can default values be overridden during insertion?

Yes, default values can be overridden by explicitly providing a different value during the insertion of a new row.

Can default values be used for existing columns in MySQL?

Yes, default values can be added to existing columns in a MySQL table using the ALTER TABLE statement.

Can the default value of a column be altered after table creation?

Yes, the default value of a column can be altered after table creation using the ALTER TABLE statement.

What happens if the default value violates a constraint?

If the default value violates a constraint (such as a check constraint or a foreign key constraint), MySQL will not allow the row to be inserted and an error will be thrown.

Can default values be set based on the values of other columns?

Yes, default values can be set based on the values of other columns by using expressions or functions in the DEFAULT clause.

Can different columns in a table have different default values?

Yes, each column in a MySQL table can have its own unique default value.

Can default values be specified for more than one column at a time?

Yes, multiple columns can have default values specified at the time of table creation or during altering the table, by separating each column with a comma.

In conclusion, the default value in MySQL is the automatically assigned value to a column if no specific value is provided during insertion. It serves the purpose of ensuring data integrity, consistency, and simplifying data entry.

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