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Database Management System
SELECT column1, column2, ...
FROM table
WHERE condition(s)
GROUP BY column(s)
HAVING condition(s)
ORDER BY column(s)
LIMIT number_of_rows
OFFSET offset_value;
It’s important to note that the clauses can be arranged in different orders depending on the query’s requirements, and not all clauses are necessary for every query. The structure and availability of SQL features may vary slightly across different database management systems.
SELECT column1, column2, ...
FROM table
WHERE condition(s)
UPDATE Statement: The UPDATE statement, on the other hand, is used to modify existing data in the database. It allows you to change the values of one or more columns in a table based on specified conditions. The UPDATE statement alters the data in the table and permanently modifies the values.
Example UPDATE statement:
UPDATE table
SET column1 = value1, column2 = value2, ...
WHERE condition(s)
Key differences between SELECT and UPDATE statements:
Purpose: SELECT is used to retrieve data, while UPDATE is used to modify data.
Data Modification: SELECT does not modify the data in the tables, whereas UPDATE statement modifies the data by changing the values of specified columns.
Result: SELECT returns a result set containing the retrieved data, while UPDATE does not return a result set by default. It typically provides a count of the affected rows.
Usage: SELECT is used for querying and retrieving data for various purposes, such as reporting and analysis. UPDATE is used when you need to change specific values in the database.
Impact: SELECT has no impact on the underlying data, while UPDATE permanently alters the data, and the changes persist in the database.
It’s important to exercise caution when using the UPDATE statement to ensure that the modifications are accurately targeted and aligned with the intended changes in the data. Always take appropriate precautions and backup data before performing updates to avoid unintended consequences.
SELECT column1, column2, ...
FROM table
WHERE condition;
Multiple conditions with logical operators:
SELECT column1, column2, ...
FROM table
WHERE condition1 AND condition2;
WHERE clause with subquery:
SELECT column1, column2, ...
FROM table
WHERE column1 IN (SELECT column FROM another_table WHERE condition);
The WHERE clause is a powerful tool that allows you to filter and retrieve specific data from the database based on your requirements. It helps in narrowing down the result set and provides control over which rows are included in the query’s output.
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