There are different datatypes used to build a column in MySQL table. For example SMALLINT, MEDIUMINT, and INT. I understand that different datatype will affect table size according to column types. Therefore, its unnecessary to assign UNSIGNED INT to a value which ranges between 0-1000.
What happens if you multiply values of different datatypes in MySQL (e.g. SMALLINT * INT)? What MySQL datatype do you need to store the result?
MySQL defines some rules for arithmetic operations.
In case of +, -, * result is calculated to BIGINT (64-bit) precision if both operands are integers (e.g. SMALLINT, INT)
If both operands are integer and any of them are UNSIGNED, the result is an unsigned integer. For subtraction (-) if NO_UNSIGNED_SUBTRACTION SQL mode is enabled, the result will be signed.
If any of the operands of a +, -, /, *, % is real (e.g. FLOAT or DOUBLE) or string value (e.g. '10.13e-3') the precision of the result is the precision of the operand with the maximum precision.
It is safe to do arithmetic operations between columns with different datatypes. MySQL will automatically convert into appropriate format.
As for storing its result, there are some constraints.
If out-of-range value is inserted, largest endpoint will be stored (e.g. inserting 130 to TINYINT will store 127 and raise warning). If strict mode is enabled, insertion will fail and raise error.
Integer overflow results in silent wraparound (e.g. 9223372036854775807 + 1 = -9223372036854775808. This is because its the largest possible operation using BIGINT datatype).
When a floating-point or fixed-point column is assigned a value that exceeds the range implied by the specified (or default) precision and scale, MySQL stores the value representing the corresponding endpoint of that range
Floating-point overflow produces NULL result. Some operation can result in +INF, -INF or `NaN'.
DECIMAL datatype, if overflowed, will be truncated. And raise warning.
References (from dev.mysql.com):
Out of range & Overflow
Arithmetic functions
Related
In a MySQL database, I have a table with a column of type varbinary(255) (CHARSET is set to binary). The values in the column loo like these:
-8999130301
NULL
-7010978
-16139671
-2
I interpret the values as signed integers.
Now I want to replace all NULL values with the minimum value for the varbinary(255) data type using the COALESCE() function.
The minimum signed integer that can be stored in a varbinary(255) attribute is "-9999..." (with 254 nines), but I do not want to hard code the value.
How can I compute the minimum value for a data type with SQL to use it in COALESCE()?
I was working on a project and due to a miscomprehension, we ended up comparing a stored int with a string in a MySql database. I ran a few test and it seems to work but I would like to know how MySql compares different datatypes.
Does it convert one to the other? If it does does it convert both to strings or to ints?
When you use a string in an integer context, for example in an arithmetic expression or in a comparison to an integer, MySQL takes the numeric value of that string as a DOUBLE data type.
See https://dev.mysql.com/doc/refman/5.7/en/type-conversion.html
Demonstration:
mysql> create table foo as select 1+'1' as x;
mysql> show create table foo\G
CREATE TABLE `foo` (
`x` double NOT NULL DEFAULT '0'
) ENGINE=InnoDB DEFAULT CHARSET=latin1
The numeric value of a string is the numeric value of any leading digit characters or other characters that make a floating-point number, like -+.e.
For example, the numeric value of '123abc' is 123.
Scientific notation is supported.
mysql> select 1 + '5e-2xyz' as n;
+------+
| n |
+------+
| 1.05 |
+------+
If there are no leading characters that form a numeric value, the string's numeric value is 0.
Mysql manual has a complete section dedicated to this, called Type Conversion in Expression Evaluation.
When an operator is used with operands of different types, type conversion occurs to make the operands compatible. Some conversions occur implicitly. For example, MySQL automatically converts numbers to strings as necessary, and vice versa.
If you compare an int with a string, then both values are converted to floating point number and compared thus.
I was trying to add a number with a length of 11 but when I input it in the database it can't. If I try to add a number with a length of 10 it can.
This is the error:
ERROR 1264: 1264: Out of range value for column 'contact_no' at row 1
SQL Statement:
INSERT INTO `mcs`.`new_table` (`id`, `contact_no`) VALUES ('1', '12345678901')
It's not clear what question you are asking.
Why is this error being returned?
Likely, the contact_no column is declared with datatype of INT, a 32-bit integer, and you attempted to assign a value larger than the supported maximum value.
The maximum value for a signed 32-bit integer is 2,147,483,647. (that decimal value of 2^31-1. For an unsigned 32-bit integer, maximum value is 2^32.)
Some other question that wasn't asked
If you need to store values larger than the maximum supported by the INT datatype, you could define the column as a different datatype.
For example, BIGINT gives a maximum value of 2^63-1 for unsigned.
If you need a maximum of 12 decimal digits, you could use a DECIMAL(12) datatype.
Change your data type of contact_no to BIGINT.
Check range of different data type at MYSQL official website.
I personally recommend you to use varchar, as you don't need to compare contact number with any field.
Please check datatype of contact_no column.
'12345678901' is exceeding its size.
I have a float data field :
`total` float(20,2) unsigned NOT NULL,
I want to insert a float number like : "815032.68" but it's not accepted and the number is rounded to 815032.69. why?
Use a fixed-point data type
`total` DECIMAL(20,2) unsigned NOT NULL
The DECIMAL and NUMERIC types store exact numeric data values. These types are used when it is important to preserve exact precision, for example with monetary data.
MySQL Doc
Floating-point data types can only store approximate numbers.
Floats are 32 bit numbers stored as mantissa and exponents,the maximum value a FLOAT can have is +8388608*10^127 and the minimum is -8388608*10^127. This means only 7 significant digits, and your FLOAT definition used 20.Use double data type.
I am inserting value
insert into user (name,fbid) Values ('Adi Mathur',100000564553314)
but in the database i see the value if fbid to be
2147483647
Why ? How should i fix it ?
fbid int(50)
As explained in the manual, the maximum value of a (signed) INT, which occupies 4 bytes/32 bits, is 2,147,483,647; for integer data types, the number in parenthesis is the display width, which only affects the way that the data is displayed, not how much space it is allocated for storage:
M indicates the maximum display width for integer types. For floating-point and fixed-point types, M is the total number of digits that can be stored (the precision). For string types, M is the maximum length. The maximum permissible value of M depends on the data type.
You probably want a BIGINT.