50 Essential SQL Operators - nTells Online Tech

Structured Query Language (SQL) is the cornerstone of managing and interacting with relational databases. SQL operators are fundamental components that allow developers and database administrators to manipulate and retrieve data effectively.

In this article, we will explore 50 essential SQL operators, categorized into different types, each serving a specific purpose in querying and modifying data.

1. Arithmetic Operators

Arithmetic operators are used to perform basic arithmetic calculations on numeric values within SQL queries.

Addition (+): Adds two numeric values.
Subtraction (-): Subtracts one numeric value from another.
Multiplication (*): Multiplies two numeric values.
Division (/): Divides one numeric value by another.
Modulus (%): Returns the remainder of a division operation.

2. Comparison Operators

Comparison operators are used to compare values in SQL queries, returning boolean results.

Equal (=): Checks if two values are equal.
Not Equal (!= or <>): Checks if two values are not equal.
Greater Than (>): Checks if one value is greater than another.
Less Than (<): Checks if one value is less than another.
Greater Than or Equal To (>=): Checks if one value is greater than or equal to another.
Less Than or Equal To (<=): Checks if one value is less than or equal to another.

3. Logical Operators

Logical operators are used to combine or negate conditions in SQL queries.

AND: Returns true if both conditions are true.
OR: Returns true if at least one condition is true.
NOT: Negates a condition, returning true if the condition is false.

4. Assignment Operators

Assignment operators are used to set values in SQL statements.

=: Assigns a value to a column.
+=: Adds a value to a column and updates it.
-=: Subtracts a value from a column and updates it.
*=: Multiplies a column by a value and updates it.
/=: Divides a column by a value and updates it.

5. String Operators

String operators are used to manipulate string values within SQL queries.

Concatenation (||): Joins two strings together.
LENGTH: Returns the length of a string.
SUBSTRING: Extracts a portion of a string.
REPLACE: Replaces occurrences of a substring within a string.
UPPER: Converts a string to uppercase.
LOWER: Converts a string to lowercase.

6. Wildcard Operators

Wildcard operators are used in conjunction with the LIKE clause to search for patterns within strings.

%: Represents zero or more characters.
_: Represents a single character.

7. Membership Operators

Membership operators are used to check if a value exists in a set of values.

IN: Checks if a value exists in a list of values.
NOT IN: Checks if a value does not exist in a list of values.

8. NULL-Related Operators

NULL-related operators are used to handle NULL values in SQL queries.

IS NULL: Checks if a value is NULL.
IS NOT NULL: Checks if a value is not NULL.

9. BETWEEN Operator

The BETWEEN operator is used to check if a value lies within a specified range.

BETWEEN value1 AND value2: Checks if a value is between the specified range.

10. EXISTS Operator

The EXISTS operator is used to check if a subquery returns any rows.

EXISTS (subquery): Returns true if the subquery returns any rows.

11. UNIQUE Operator

The UNIQUE operator enforces that all values in a column are unique.

UNIQUE: Specifies that values in a column must be unique.

12. DISTINCT Operator

The DISTINCT operator removes duplicate rows from the result set.

SELECT DISTINCT column1, column2 FROM table_name;

13. ORDER BY Operator

The ORDER BY operator is used to sort the result set based on specified columns.

ORDER BY column1 ASC/DESC, column2 ASC/DESC;

14. GROUP BY Operator

The GROUP BY operator is used to group rows based on specified columns for aggregation.

GROUP BY column1, column2;

15. HAVING Operator

The HAVING operator is used to filter results after using the GROUP BY clause.

HAVING aggregate_function(column) condition;

16. JOIN Operators

JOIN operators are used to combine rows from multiple tables based on a related column.

INNER JOIN: Returns rows with matching values in both tables.
LEFT JOIN (or LEFT OUTER JOIN): Returns all rows from the left table and matching rows from the right table.
RIGHT JOIN (or RIGHT OUTER JOIN): Returns all rows from the right table and matching rows from the left table.
FULL JOIN (or FULL OUTER JOIN): Returns all rows when there is a match in either the left or right table.

17. UNION Operator

The UNION operator combines the result sets of two or more SELECT statements, removing duplicates.

SELECT column1 FROM table1 UNION SELECT column1 FROM table2;

18. INTERSECT Operator

The INTERSECT operator returns common rows between two SELECT statements.

SELECT column1 FROM table1 INTERSECT SELECT column1 FROM table2;

19. EXCEPT Operator

The EXCEPT operator returns rows from the first SELECT statement that do not exist in the second SELECT statement.

SELECT column1 FROM table1 EXCEPT SELECT column1 FROM table2;

20. ANY and ALL Operators

The ANY and ALL operators are used with subqueries and comparison operators.

ANY: Returns true if the comparison is true for at least one value.
ALL: Returns true if the comparison is true for all values.

21. EXISTS vs. IN

Both EXISTS and IN are used to check if a subquery returns any rows, but they have subtle differences.

EXISTS (subquery): Returns true if the subquery returns any rows.
value IN (subquery): Checks if a value exists in the result set of the subquery.

22. LIKE Operator

The LIKE operator is used to search for a specified pattern in a column.

SELECT column1 FROM table WHERE column2 LIKE pattern;

23. NOT LIKE Operator

The NOT LIKE operator is used to exclude rows that match a specified pattern.

SELECT column1 FROM table WHERE column2 NOT LIKE pattern;

24. LIMIT and OFFSET Operators

The LIMIT operator is used to limit the number of rows returned, while the OFFSET operator skips a specified number of rows.

SELECT column1 FROM table LIMIT count OFFSET offset;

25. CASE Operator

The CASE operator performs conditional logic within SQL queries.

CASE WHEN condition THEN result END;

26. COALESCE Operator

The COALESCE operator returns the first non-NULL value from a list of values.

COALESCE(value1, value2, …);

27. NULLIF Operator

The NULLIF operator returns NULL if two values are equal, otherwise returns the first value.

NULLIF(value1, value2);

28. CAST and CONVERT Operators

The CAST and CONVERT operators are used to convert data types.

CAST(column AS new_data_type);
CONVERT(new_data_type, column);

29. ROW_NUMBER() Function

The ROW_NUMBER() function assigns a unique sequential integer to each row in a result set.

ROW_NUMBER() OVER (ORDER BY column);

30. RANK() Function

The RANK() function assigns a unique rank to rows with the same values in specified columns.

RANK() OVER (ORDER BY column);

31. DENSE_RANK() Function

The DENSE_RANK() function assigns a unique rank to rows with the same values in specified columns, without gaps.

DENSE_RANK() OVER (ORDER BY column);

32. NTILE() Function

The NTILE() function divides the result set into specified number of tiles, assigning a tile number to each row.

NTILE(number) OVER (ORDER BY column);

33. LAG() Function

The LAG() function returns the value from a previous row in the result set.

LAG(column, offset) OVER (ORDER BY column);

34. LEAD() Function

The LEAD() function returns the value from a following row in the result set.

LEAD(column, offset) OVER (ORDER BY column);

35. SUM() Function

The SUM() function calculates the sum of values in a column.

SUM(column) OVER (PARTITION BY partition_column);

36. AVG() Function

The AVG() function calculates the average of values in a column.

AVG(column) OVER (PARTITION BY partition_column);

37. MIN() Function

The MIN() function returns the minimum value in a column.

MIN(column) OVER (PARTITION BY partition_column);

38. MAX() Function

The MAX() function returns the maximum value in a column.

MAX(column) OVER (PARTITION BY partition_column);

39. COUNT() Function

The COUNT() function counts the number of rows in a result set or a column.

COUNT(*) OVER (PARTITION BY partition_column);

40. FIRST_VALUE() Function

The FIRST_VALUE() function returns the value of the first row in a window frame.

FIRST_VALUE(column) OVER (ORDER BY column);

41. LAST_VALUE() Function

The LAST_VALUE() function returns the value of the last row in a window frame.

LAST_VALUE(column) OVER (ORDER BY column);

42. TOP Operator

The TOP operator retrieves a specified number or percentage of rows from a result set.

SELECT TOP number column FROM table;

43. CROSS APPLY Operator

The CROSS APPLY operator applies a table-valued function to each row and returns the result set.

SELECT column FROM table CROSS APPLY function;

44. OUTER APPLY Operator

The OUTER APPLY operator applies a table-valued function to each row and returns even if the function returns no results.

SELECT column FROM table OUTER APPLY function;

45. FOR XML Operator

The FOR XML operator formats query results as XML.

SELECT column FROM table FOR XML AUTO;

46. PIVOT Operator

The PIVOT operator transforms rows into columns based on the values in a specified column.

SELECT * FROM table PIVOT (aggregate_function(column) FOR pivot_column IN (…) ) AS pivoted_table;

47. UNPIVOT Operator

The UNPIVOT operator transforms columns into rows.

SELECT unpivoted_column, value FROM table UNPIVOT (value FOR unpivoted_column IN (…) ) AS unpivoted_table;

48. MERGE Operator

The MERGE operator combines INSERT, UPDATE, and DELETE operations into a single statement.

MERGE INTO target_table USING source_table ON condition WHEN MATCHED THEN UPDATE … WHEN NOT MATCHED THEN INSERT …;

49. TRUNCATE TABLE Operator

The TRUNCATE TABLE operator removes all rows from a table without logging individual row deletions.

TRUNCATE TABLE table;

50. DELETE Operator

The DELETE operator removes rows from a table based on specified conditions.

DELETE FROM table WHERE condition;

Conclusion

SQL operators are the building blocks of powerful and versatile database querying and manipulation. Whether you’re performing basic calculations, comparing values, joining tables, or applying complex functions, the extensive range of SQL operators equips you with the tools to extract meaningful insights from your data.

This comprehensive guide to 50 essential SQL operators provides a solid foundation for mastering the art of database querying and manipulation, enabling you to harness the full potential of relational databases for your applications and projects.