MySQL :: MySQL 8.4 Reference Manual :: 14.6.1 Arithmetic Operators (original) (raw)

14.6.1 Arithmetic Operators

Table 14.9 Arithmetic Operators

The usual arithmetic operators are available. The result is determined according to the following rules:

• In the case of-,+, and*, the result is calculated with BIGINT (64-bit) precision if both operands are integers.
• If both operands are integers and any of them are unsigned, the result is an unsigned integer. For subtraction, if theNO_UNSIGNED_SUBTRACTION SQL mode is enabled, the result is signed even if any operand is unsigned.
• If any of the operands of a+,-,/,*,% is a real or string value, the precision of the result is the precision of the operand with the maximum precision.
• In division performed with/, the scale of the result when using two exact-value operands is the scale of the first operand plus the value of thediv_precision_increment system variable (which is 4 by default). For example, the result of the expression 5.05 / 0.014 has a scale of six decimal places (360.714286).

These rules are applied for each operation, such that nested calculations imply the precision of each component. Hence,(14620 / 9432456) / (24250 / 9432456), resolves first to (0.0014) / (0.0026), with the final result having 8 decimal places (0.60288653).

Because of these rules and the way they are applied, care should be taken to ensure that components and subcomponents of a calculation use the appropriate level of precision. SeeSection 14.10, “Cast Functions and Operators”.

For information about handling of overflow in numeric expression evaluation, see Section 13.1.7, “Out-of-Range and Overflow Handling”.

Arithmetic operators apply to numbers. For other types of values, alternative operations may be available. For example, to add date values, use DATE_ADD(); see Section 14.7, “Date and Time Functions”.

• +
  Addition:

mysql> SELECT 3+5;  
        -> 8  

• -
  Subtraction:

mysql> SELECT 3-5;  
        -> -2  

• -
  Unary minus. This operator changes the sign of the operand.

mysql> SELECT - 2;  
        -> -2  

Note
If this operator is used with aBIGINT, the return value is also a BIGINT. This means that you should avoid using - on integers that may have the value of −263.

• *
  Multiplication:

mysql> SELECT 3*5;  
        -> 15  
mysql> SELECT 18014398509481984*18014398509481984.0;  
        -> 324518553658426726783156020576256.0  
mysql> SELECT 18014398509481984*18014398509481984;  
        -> out-of-range error  

The last expression produces an error because the result of the integer multiplication exceeds the 64-bit range ofBIGINT calculations. (SeeSection 13.1, “Numeric Data Types”.)

• /
  Division:

mysql> SELECT 3/5;  
        -> 0.60  

Division by zero produces a NULL result:

mysql> SELECT 102/(1-1);  
        -> NULL  

A division is calculated withBIGINT arithmetic only if performed in a context where its result is converted to an integer.

• DIV
  Integer division. Discards from the division result any fractional part to the right of the decimal point.
  If either operand has a noninteger type, the operands are converted to DECIMAL and divided using DECIMAL arithmetic before converting the result toBIGINT. If the result exceedsBIGINT range, an error occurs.

mysql> SELECT 5 DIV 2, -5 DIV 2, 5 DIV -2, -5 DIV -2;  
        -> 2, -2, -2, 2  

• N % M,N MOD M
  Modulo operation. Returns the remainder of_N_ divided by_M_. For more information, see the description for the MOD() function in Section 14.6.2, “Mathematical Functions”.