SQL Operators
SQL operators comprise operators for comparing, calculating, evaluating and concatenating values.
SQL operators comprise operators for comparing, calculating, evaluating and concatenating values.
SQL Operators are divided into four types.Each operator type has a precedence, a ranking that determines the order in which operators and the values obtained with their help are evaluated in an expression.The higher the precedence of the operator type is, the earlier it will be evaluated.Each operator has its own precedence within its type, that determines the order in which they are evaluated in an expression.
Operators with the same precedence are evaluated from left to right.To force a different evaluation order, operations can be grouped by means of parentheses.
Operator Type  Precedence  Explanation 

Concatenation 
1 
Strings are concatenated before any other operations take place 
Arithmetic 
2 
Arithmetic operations are performed after strings are concatenated, but before comparison and logical operations 
Comparison 
3 
Comparison operations take place after string concatenation and arithmetic operations, but before logical operations 
Logical 
4 
Logical operators are executed after all other types of operators 
The concatenation operator — two pipe characters known as “double pipe” or ‘
’ — concatenates two character strings to form a single string.Character strings can be literals or values obtained from columns or other expressions.
SELECT LAST_NAME  ', '  FIRST_NAME AS FULL_NAME
FROM EMPLOYEE
Operator  Purpose  Precedence 


Unary plus 
1 

Unary minus 
1 

Multiplication 
2 

Division 
2 

Addition 
3 

Subtraction 
3 
UPDATE T
SET A = 4 + 1/(BC)*D
Note

Where operators have the same precedence, they are evaluated in lefttoright sequence. 