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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