What is the SELECT operator in SQL?

The SELECT operator is used to retrieve data from one or more tables in a database.

Its main functions:

• Selecting specific columns.
• Selecting all columns.
• Filtering rows using WHERE.
• Sorting data using ORDER BY.
• Grouping data using GROUP BY and aggregate functions.
• Combining data from multiple tables using JOIN.
• Limiting the number of returned rows (LIMIT / TOP).

Basic syntax:

-- Select all columns from a table
SELECT *
FROM table_name;

-- Select specific columns from a table
SELECT column1, column2
FROM table_name;

Extended syntax may include:

SELECT column1, column2, aggregate_function(column3)
FROM table1
-- Join with another table
JOIN table2 ON table1.matching_column = table2.matching_column
-- Filter rows
WHERE filter_condition
-- Group by columns
GROUP BY column1, column2
-- Filter groups
HAVING group_filter_condition
-- Sort results
ORDER BY sort_column ASC/DESC
-- Limit number of rows (syntax may vary across DBMS)
LIMIT number_of_rows;