What restrictions exist for defining column properties in a database?
sobes.tech AI
Answer from AI
When defining column properties in a database, the following constraints exist:
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Data type: a column must have a specific data type (e.g., INT, VARCHAR, DATE), which limits the format and size of stored data.
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Size: for some types (e.g., VARCHAR), a maximum length is set.
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NULL/NOT NULL: you can specify whether the column allows NULL values.
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Uniqueness: a uniqueness constraint (UNIQUE) can be set so that values in the column do not repeat.
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Keys: primary key (PRIMARY KEY) or foreign key (FOREIGN KEY) impose constraints on values and relationships with other tables.
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Default values: a DEFAULT value can be set, which will be used if no value is specified during data insertion.
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Checks: some DBMSs allow setting conditions that values in the column must satisfy.
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Auto-increment: for numeric columns, automatic increment of the value can be set when adding new records.
These constraints help ensure data integrity and correctness in the database.