SQL Expression

When we use two or more than two combinations of values, operators and SQL functions, then it is considered as an expression. We write an expression as a statement or query which act as a formula to show some output. We often use various expressions to query a database.

Expression Syntax

SELECT column_name_1, column_name_2, column_name_N
FROM table_name
WHERE [EXPRESSION];

We can apply expression on Different data types which include:

• Boolean
• Numeric
• Date

Boolean Expression

In boolean expression we write expression on the basis of the boolean values 0(true) and 1 (false), and we get only true values as query result. Syntax

SELECT column_name_1, column_name_2, column_name_N
FROM table_name
WHERE value match [boolean EXPRESSION];

Example Consider this table as Students:

+----+----------+-----+-------+------+
|Rank| NAME     | AGE | Grade | Marks|
+----+----------+-----+-------+------+
|  1 | Luffy    |  18 | A     |  976 |
|  2 | Naruto   |  16 | A     |  970 |
|  3 | Goku     |  20 | A     |  970 |
|  4 | Zoro     |  26| B      |  890 |
|  5 | Asta     |  16 | B     |  860 |
|  6 | Robin    |  24 |B      |  850 |
|  7 | Gohan    |  18 | C     |  845 |
+----+----------+-----+-------+------+

SELECT * FROM Students WHERE marks = 970;

Output

+----+----------+-----+-----------+----------+
|Rank|  NAME    | AGE | Grade     | Marks    |
+----+----------+-----+-----------+----------+
|  2 | Naruto   |  16 | A         |  970     |
|  3 | Goku     |  20 | A         |  970     |
+----+----------+-----+-----------+----------+

Numeric Expression

We use Numeric Expression to perform the Arithmetic Operations. Syntax

SELECT Numeric_Expression AS Custom_Column_Name;

Example

SELECT (17+20) AS add;

Output

 +----------+
| add       |
+----------+
|       37 |
+----------+

Date Expression

Date Expression are used to show the time and date related outputs. Example

select CURRENT_TIMESTAMP;

Output

+---------------------+
| CURRENT_TIMESTAMP   |
+---------------------
| 2020-03-29 13:38:43 |
+---------------------+
1 row in set (0.05 sec)

SQL Expression Quick Summary

• An expression is a query statement that is a combination of one or more than one value, Operators and SQL Functions.
• In SQL we have 3 major Expressions, Boolean, Numeric and Date.
• Boolean Expression deals with the logical and comparison operators where we have results in true and false.
• Numeric Expressions work with Arithmetic Operators.
• Date Expression Work with Date and time data types.

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