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📜  SQL-运算符

📅  最后修改于: 2020-12-29 04:30:57             🧑  作者: Mango

SQL中的运算符是什么?

运算符是保留字或字符，主要用于SQL语句的WHERE子句中以执行操作，例如比较和算术运算。这些运算符用于指定SQL语句中的条件，并用作语句中多个条件的结合。

  • 算术运算运算符
  • 运算符
  • 逻辑运算符
  • 运算符用于否定条件

SQL算术运算符

假设“变量a”持有10，而“变量b”持有20，则-

显示范例

Operator Description Example
+ (Addition) Adds values on either side of the operator. a + b will give 30
– (Subtraction) Subtracts right hand operand from left hand operand. a – b will give -10
* (Multiplication) Multiplies values on either side of the operator. a * b will give 200
/ (Division) Divides left hand operand by right hand operand. b / a will give 2
% (Modulus) Divides left hand operand by right hand operand and returns remainder. b % a will give 0

SQL比较运算符

假设“变量a”持有10，而“变量b”持有20，则-

显示范例

Operator Description Example
= Checks if the values of two operands are equal or not, if yes then condition becomes true. (a = b) is not true.
!= Checks if the values of two operands are equal or not, if values are not equal then condition becomes true. (a != b) is true.
<> Checks if the values of two operands are equal or not, if values are not equal then condition becomes true. (a <> b) is true.
> Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. (a > b) is not true.
< Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. (a < b) is true.
>= Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. (a >= b) is not true.
<= Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. (a <= b) is true.
!< Checks if the value of left operand is not less than the value of right operand, if yes then condition becomes true. (a !< b) is false.
!> Checks if the value of left operand is not greater than the value of right operand, if yes then condition becomes true. (a !> b) is true.

SQL逻辑运算符

这是SQL中可用的所有逻辑运算符的列表。

显示范例

Sr.No. Operator & Description
1

ALL

The ALL operator is used to compare a value to all values in another value set.
2

AND

The AND operator allows the existence of multiple conditions in an SQL statement’s WHERE clause.
3

ANY

The ANY operator is used to compare a value to any applicable value in the list as per the condition.
4

BETWEEN

The BETWEEN operator is used to search for values that are within a set of values, given the minimum value and the maximum value.
5

EXISTS

The EXISTS operator is used to search for the presence of a row in a specified table that meets a certain criterion.
6

IN

The IN operator is used to compare a value to a list of literal values that have been specified.
7

LIKE

The LIKE operator is used to compare a value to similar values using wildcard operators.
8

NOT

The NOT operator reverses the meaning of the logical operator with which it is used. Eg: NOT EXISTS, NOT BETWEEN, NOT IN, etc. This is a negate operator.
9

OR

The OR operator is used to combine multiple conditions in an SQL statement’s WHERE clause.
10

IS NULL

The NULL operator is used to compare a value with a NULL value.
11

UNIQUE

The UNIQUE operator searches every row of a specified table for uniqueness (no duplicates).