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Questions and Answers
What SQL keyword is used to change an attribute's definition without renaming it?
What SQL keyword is used to change an attribute's definition without renaming it?
- CHANGE
- ALTER
- MODIFY (correct)
- UPDATE
Which statement correctly changes the fax attribute to a new name and data type in the Personnes table?
Which statement correctly changes the fax attribute to a new name and data type in the Personnes table?
- ALTER TABLE Personnes CHANGE fax num_fax VARCHAR(14); (correct)
- ALTER TABLE Personnes RENAME fax TO num_fax VARCHAR(14);
- UPDATE TABLE Personnes SET fax = num_fax VARCHAR(14);
- MODIFY TABLE Personnes CHANGE fax num_fax VARCHAR(14);
What is a potential risk when changing the data type of an attribute?
What is a potential risk when changing the data type of an attribute?
- Only char types are allowed.
- The attribute name must be the same.
- Existing values might be reset to zero. (correct)
- New attributes cannot be added.
Which SQL command would correctly change the fax column's data type to a larger size without renaming it?
Which SQL command would correctly change the fax column's data type to a larger size without renaming it?
If you want to use the ALTER TABLE statement to change the definition of fax to num_fax, which aspects must be specified?
If you want to use the ALTER TABLE statement to change the definition of fax to num_fax, which aspects must be specified?
Flashcards
ALTER TABLE MODIFY
ALTER TABLE MODIFY
Modifies an attribute's data type without changing its name in a database table.
ALTER TABLE CHANGE
ALTER TABLE CHANGE
Modifies an attribute's name and data type simultaneously in a database table.
ALTER TABLE
ALTER TABLE
A SQL statement used to alter the structure of a database table, including attribute definitions.
Data type
Data type
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Data Loss
Data Loss
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Study Notes
Changing Attribute Definition
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To change an attribute definition without renaming it, use ALTER TABLE relation MODIFY attribut definition_relative
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Example: ALTER TABLE Personnes MODIFY fax VARCHAR(14)
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To change an attribute definition and rename it, use ALTER TABLE relation CHANGE attribut definition_absolue
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Example: ALTER TABLE Personnes CHANGE fax num_fax VARCHAR(14)
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Caution: If the new data type is incompatible with existing values in the table, those values might be modified or set to zero.
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