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Questions and Answers
What is the purpose of the WHERE clause in a SQL UPDATE statement?
What is the purpose of the WHERE clause in a SQL UPDATE statement?
- To limit the number of records modified
- To indicate the new values for the attributes
- To specify the records to be modified (correct)
- To specify the attributes to be modified
What does the LOW_PRIORITY option do in an UPDATE statement?
What does the LOW_PRIORITY option do in an UPDATE statement?
- It prevents any modifications from occurring
- It allows modifications only when no one is reading the relation (correct)
- It limits the number of records modified in the update
- It ensures that modifications occur immediately
In the syntax of an UPDATE statement, which part indicates the new values that attributes will take?
In the syntax of an UPDATE statement, which part indicates the new values that attributes will take?
- LIMIT clause
- SET clause (correct)
- UPDATE clause
- WHERE clause
What does the LIMIT clause do in an UPDATE statement?
What does the LIMIT clause do in an UPDATE statement?
Which SQL command would correctly modify Martin Pierre's phone number?
Which SQL command would correctly modify Martin Pierre's phone number?
Flashcards
UPDATE
UPDATE
The SQL command used to change the values in existing records (rows) within a table.
WHERE clause
WHERE clause
In an UPDATE statement, this clause specifies the conditions that must be met for the record to be updated. It acts as a filter.
SET clause
SET clause
In an UPDATE statement, this clause specifies the attributes (columns) that need to be updated and their new values.
LOW_PRORITY
LOW_PRORITY
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LIMIT clause
LIMIT clause
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Study Notes
Modifying Records
- To modify one or more records in a database relation, specify a selection criterion for the records to be changed (WHERE clause).
- Indicate the attributes whose values will be changed and their new values (SET clause).
Syntax
-
UPDATE [LOW_PRIORITY] [relation] SET [attribute=value, ...] [WHERE [condition]] [LIMIT n] -
LOW_PRIORITY: An option that allows the update to be performed only once other reads are finished.
Example
- Changing Martin Pierre's phone number:
UPDATE TABLE Personnes SET telephone='0156281469' WHERE nom='Martin' AND prenom = 'Pierre'
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