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MYSQL DATAT TYPES EXPLANATION?

MYSQL DATAT TYPES EXPLANATION?


What is data type

1. A data type specifies a particular type of data, such as integer, floating-point, Boolean etc.

2. A data type also specifies the possible values for that type, the operations that can be performed on that type and the way the values of that type are stored.
MySQL data types

MySQL supports a number of SQL standard data types in various categories. MySQL has Numeric Types, the DATETIME, DATE, and TIMESTAMP Types and String Types. Data types are discussed on this page are based on MySQL community server 5.6
MySQL Numeric Types

MySQL supports all standard SQL numeric data types which include INTEGER, SMALLINT, DECIMAL, and NUMERIC. It also supports the approximate numeric data types (FLOAT, REAL, and DOUBLE PRECISION). The keyword INT is a synonym for INTEGER, and the keywords DEC and FIXED are synonyms for DECIMAL. DOUBLE is a synonym for DOUBLE PRECISION (a nonstandard extension). REAL is a synonym for DOUBLE PRECISION (a nonstandard variation), unless the REAL_AS_FLOAT SQL mode is enabled. The BIT data type stores bit-field values and is supported for MyISAM, MEMORY, InnoDB, and NDB tables.
Integer types

SQL standard integer types INTEGER (or INT) and SMALLINT are supported by MySQL. As an extension to the standard, MySQL also supports the integer types TINYINT, MEDIUMINT, and BIGINT. Following table shows the required storage and range (maximum and minimum value for signed and unsigned integer) for each integer type.
Type     Length
in Bytes     Minimum Value
(Signed)     Maximum Value
(Signed)     Minimum Value
(Unsigned)     Maximum Value
(Unsigned)
TINYINT     1     -128     127     0     255
SMALLINT     2     -32768     32767     0     65535
MEDIUMINT     3     -8388608     8388607 to     0     16777215
INT     4     -2147483648     2147483647     0     4294967295
BIGINT     8     -9223372036854775808     92233720368
54775807     0     184467440737
09551615
Floating-Point Types

The FLOAT and DOUBLE types represent approximate numeric data values. MySQL uses four bytes for single-precision values and eight bytes for double-precision values.
Types     Description
FLOAT     A precision from 0 to 23 results in a four-byte single-precision FLOAT column
DOUBLE     A precision from 24 to 53 results in an eight-byte double-precision DOUBLE column.

MySQL allows a nonstandard syntax: FLOAT(M,D) or REAL(M,D) or DOUBLE PRECISION(M,D). Here values can be stored up to M digits in total where D represents the decimal point. For example, a column defined as FLOAT(8,5) will look like -999.99999. MySQL performs rounding when storing values, so if you insert 999.00009 into a FLOAT(7,4) column, the approximate result is 999.0001.

Following table shows the required storage and range (maximum and minimum value for signed and unsigned integer) for each floating-point type.
Type     Length
in Bytes     Minimum Value
(Signed)     Maximum Value
(Signed)     Minimum Value
(Unsigned)     Maximum Value
(Unsigned)
FLOAT     4     -3.402823466E+38      -1.175494351E-38      1.175494351E-38      3.402823466E+38
DOUBLE     8     -1.7976931348623
157E+ 308     -2.22507385850720
14E- 308     0, and
2.22507385850720
14E- 308      1.797693134862315
7E+ 308
Fixed-Point Types

Fixed-Point data types are used to preserve exact precision, for example with currency data. In MySQL DECIMAL and NUMERIC types store exact numeric data values. MySQL 5.6 stores DECIMAL values in binary format.

In standard SQL the syntax DECIMAL(5,2)  (where 5 is the precision and 2 is the scale. ) be able to store any value with five digits and two decimals. Therefore the value range will be from -999.99 to 999.99. The syntax DECIMAL(M) is equivalent to DECIMAL(M,0). Similarly, the syntax DECIMAL is equivalent to DECIMAL(M,0). MySQL supports both of these variant forms of DECIMAL syntax. The default value of M is 10. If the scale is 0, DECIMAL values contain no decimal point or fractional part.
The maximum number of digits for DECIMAL is 65, but the actual range for a given DECIMAL column can be constrained by the precision or scale for a given column.
Bit Value Types

The BIT data type is used to store bit-field values. A type of BIT(N) enables storage of N-bit values. N can range from 1 to 64.
To specify bit values, b'value' notation can be used. value is a binary value written using zeros and ones. For example, b'111' and b'10000000' represent 7 and 128, respectively
Numeric type attributes

MySQL supports an extension for optionally specifying the display width of integer data types in parentheses following the base keyword for the type
Types     Description
TYPE(N)     Where N is an integer and display width of the type is upto N digits.
ZEROFILL     The default padding of spaces is replaced with zeros. So, for a column INT(3) ZEROFILL, 7 is displayed as 007.
MySQL Date and Time Types

The date and time types represents DATE, TIME, DATETIME, TIMESTAMP, and YEAR. Each type has a range of valid values, as well as a “zero” value.
DATETIME, DATE, and TIMESTAMP Types
Types     Description     Display Format     Range
DATETIME     Use when you need values containing both date and time information.     YYYY-MM-DD HH:MM:SS     '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.
DATE     Use when you need only date information.     YYYY-MM-DD     '1000-01-01' to '9999-12-31'.
TIMESTAMP     Values are converted from the current time zone to UTC while storing, and converted back from UTC to the current time zone when retrieved.     YYYY-MM-DD HH:MM:SS     '1970-01-01 00:00:01' UTC to '2038-01-19 03:14:07' UTC
Time Type

MySQL fetches and displays TIME values in 'HH:MM:SS' format or 'HHH:MM:SS' format The range of. TIME values from '-838:59:59' to '838:59:59'. The hours part may be rather large because not only the TIME type can be used to represent the time of day, i.e. less than 24 hours, but also the passed time or a time of interval between two events.

The TIME values in MySQL can be recognizes in many different formats, some of which can include a trailing fractional seconds part in up to 6 digits microseconds precision. The range for TIME values is '-838:59:59.000000' to '838:59:59.000000'.

MySQL explain abbreviated TIME values with colons as the time of the day. Suppose '09:10' means '09:10:00', not '00:09:10'. MySQL understand the abbreviated values without colons as that, the two rightmost digits represent seconds. For example, we think of '0910' and 0910 as meaning '09:10:00', i.e. 10 minutes after 9 o'clock but the reality is MySQL understand them as '00:09:10', i.e. 9 minutes and 10 seconds. So, be careful about using abbreviated time in MySQL.

By default, the values of time that lies outside the TIME are converted to the valid range of time values. For example, '-930:00:00' and '930:00:00' are converted to '-838:59:59' and '838:59:59'. Invalid TIME values are converted to '00:00:00', because '00:00:00' is itself a valid TIME value in MySQL.
Year Type

The YEAR type is a 1-byte type used to represent year values. It can be declared as YEAR(2) or YEAR(4) to specify a display width of two or four characters. If no width is given the default is four characters

YEAR(4) and YEAR(2) have different display format, but have the same range of values.
For 4-digit format, MySQL displays YEAR values in YYYY format, with a range of 1901 to 2155, or 0000.
For 2-digit format, MySQL displays only the last two (least significant) digits; for example, 70 (1970 or 2070) or 69 (2069).

You can specify YEAR values in a variety of formats:
String length     Range
4-digit string     '1901' to '2155'.
4-digit number     1901 to 2155.
1- or 2-digit string     '0' to '99'. Values in the ranges '0' to '69' and '70' to '99' are converted to YEAR values in the ranges 2000 to 2069 and 1970 to 1999.
1- or 2-digit number     1 to 99. Values in the ranges 1 to 69 and 70 to 99 are converted to YEAR values in the ranges 2001 to 2069 and 1970 to 1999.
String Types

The string types are CHAR, VARCHAR, BINARY, VARBINARY, BLOB, TEXT, ENUM, and SET.
CHAR and VARCHAR Types

The CHAR and VARCHAR types are similar, but differ in the way they are stored and retrieved. They also differ in maximum length and in whether trailing spaces are retained.
Types     Description     Display Format     Range in characters
CHAR     Contains non-binary strings. Length is fixed as you declare while creating a table. When stored, they are right-padded with spaces to the specified length.     Trailing spaces are removed.     The length can be any value from 0 to 255.
VARCHAR     Contains non-binary strings. Columns are variable-length strings.     As stored.     A value from 0 to 255 before MySQL 5.0.3, and 0 to 65,535 in 5.0.3 and later versions.
BINARY and VARBINARY Types

The BINARY and VARBINARY types are similar to CHAR and VARCHAR, except that they contain binary strings rather than nonbinary strings.
Types     Description     Range in bytes
BINARY     Contains binary strings.     0 to 255
VARBINARY     Contains binary strings.     A value from 0 to 255 before MySQL 5.0.3, and 0 to 65,535 in 5.0.3 and later versions.
BLOB and TEXT Types

A BLOB is a binary large object that can hold a variable amount of data. There are four types of BLOB, TINYBLOB, BLOB, MEDIUMBLOB, and LONGBLOB. These differ only in the maximum length of the values they can hold.
The four TEXT types are TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT. These correspond to the four BLOB types and have the same maximum lengths and storage requirements.
Types     Description     Categories     Range
BLOB     Large binary object that containing a variable amount of data. Values are treated as binary strings.You don't need to specify length while creating a column.     TINYBLOB     Maximum length of 255 characters.
MEDIUMBLOB     Maximum length of 16777215 characters.
LONGBLOB     Maximum length of 4294967295 characters
TEXT     Values are treated as character strings having a character set.     TINYBLOB     Maximum length of 255 characters.
MEDIUMBLOB     Maximum length of 16777215 characters.
LONGBLOB     Maximum length of 4294967295 characters
ENUM Types

A string object whose value is chosen from a list of values given at the time of table creation. For example -
CREATE TABLE length ( length ENUM('small', 'medium', 'large') );

SET Types

A string object having zero or more comma separated values (maximum 64). Values are chosen from a list of values given at the time of table creation.
Difference between MySQL Datetime and Timestamp data Types

The DATETIME type is used when you need values containing both date and time information. MySQL retrieves and displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format. The supported range is 1000-01-01 00:00:00' to '9999-12-31 23:59:59'.

The TIMESTAMP data type is also used when you need values containing both date and time information. TIMESTAMP has a range of '1970-01-01 00:00:01' UTC to '2038-01-19 03:14:07' UTC

The major difference between DATETIME and TIMESTAMP is that TIMESTAMP values are converted from the current time zone to UTC while storing, and converted back from UTC to the current time zone when retrieved. The datetime data type value is unchanged.

See the following example :

The following command displays current time zone information :

show variable timezone

Let create a table with two fields udatetime (data type -> datetime) utimestamp (data type -> timestamp) and insert one record with now() (returns the current date and time) as a value in both fields.

mysql> create table tempdate (udatetime datetime, utimestamp timestamp);
Query OK, 0 rows affected (0.32 sec)

mysql> insert into tempdate values ((now()), (now()));
Query OK, 1 row affected (0.05 sec)

Now see the records;

At this point the datetime and timestamp data types have same values.

select all from tempdata

In the above output both the fields have same values. Let change the timezone and see the result.

mysql> SET TIME_ZONE ='Europe/Paris';
Query OK, 0 rows affected (0.00 sec)

Now execute the following command :

mysql> select * from tempdate;
+---------------------+---------------------+
| udatetime           | utimestamp          |
+---------------------+---------------------+
| 2013-06-29 16:55:18 | 2013-06-29 13:25:18 |
+---------------------+---------------------+
1 row in set (0.00 sec)



TEXT TYPES
CHAR( )    A fixed section from 0 to 255 characters long.
VARCHAR( )    A variable section from 0 to 255 characters long.
TINYTEXT    A string with a maximum length of 255 characters.
TEXT    A string with a maximum length of 65535 characters.
BLOB    A string with a maximum length of 65535 characters.
MEDIUMTEXT    A string with a maximum length of 16777215 characters.
MEDIUMBLOB    A string with a maximum length of 16777215 characters.
LONGTEXT    A string with a maximum length of 4294967295 characters.
LONGBLOB    A string with a maximum length of 4294967295 characters.

The ( ) brackets allow you to enter a maximum number of characters will be used in the column.
VARCHAR(20)

CHAR and VARCHAR are the most widely used types. CHAR is a fixed length string and is mainly used when the data is not going to vary much in it's length. VARCHAR is a variable length string and is mainly used when the data may vary in length.

CHAR may be faster for the database to process considering the fields stay the same length down the column. VARCHAR may be a bit slower as it calculates each field down the column, but it saves on memory space. Which one to ultimatly use is up to you.

Using both a CHAR and VARCHAR option in the same table, MySQL will automatically change the CHAR into VARCHAR for compatability reasons.

BLOB stands for Binary Large OBject. Both TEXT and BLOB are variable length types that store large amounts of data. They are similar to a larger version of VARCHAR. These types can store a large piece of data information, but they are also processed much slower.

NUMBER TYPES
TINYINT( )    -128 to 127 normal
0 to 255 UNSIGNED.
SMALLINT( )    -32768 to 32767 normal
0 to 65535 UNSIGNED.
MEDIUMINT( )    -8388608 to 8388607 normal
0 to 16777215 UNSIGNED.
INT( )    -2147483648 to 2147483647 normal
0 to 4294967295 UNSIGNED.
BIGINT( )    -9223372036854775808 to 9223372036854775807 normal
0 to 18446744073709551615 UNSIGNED.
FLOAT    A small number with a floating decimal point.
DOUBLE( , )    A large number with a floating decimal point.
DECIMAL( , )    A DOUBLE stored as a string , allowing for a fixed decimal point.

The integer types have an extra option called UNSIGNED. Normally, the integer goes from an negative to positive value. Using an UNSIGNED command will move that range up so it starts at zero instead of a negative number.

DATE TYPES
DATE    YYYY-MM-DD.
DATETIME    YYYY-MM-DD HH:MM:SS.
TIMESTAMP    YYYYMMDDHHMMSS.
TIME    HH:MM:SS.

MISC TYPES
ENUM ( )    Short for ENUMERATION which means that each column may have one of a specified possible values.
SET    Similar to ENUM except each column may have more than one of the specified possible values.

ENUM is short for ENUMERATED list. This column can only store one of the values that are declared in the specified list contained in the ( ) brackets.
ENUM('y','n')
You can list up to 65535 values in an ENUM list. If a value is inserted that is not in the list, a blank value will be inserted.

SET is similar to ENUM except SET may contain up to 64 list items and can store more than one choice.

MySQL supports a number of column types, which may be grouped into three categories: numeric types, date and time types, and string (character) types. This section first gives an overview of the types available. Please refer to the MySQL manuals for more details.

Type
    Use for
    Size
TINYINT
    A very small integer
    The signed range is –128 to 127. The unsigned range is 0 to 255.
SMALLINT
    A small integer
    The signed range is –32768 to 32767. The unsigned range is 0 to 65535
MEDIUMINT
    A medium-size integer
    The signed range is –8388608 to 8388607. The unsigned range is 0 to 16777215
INT or INTEGER
    A normal-size integer
    The signed range is –2147483648 to 2147483647. The unsigned range is 0 to 4294967295
BIGINT
    A large integer
    The signed range is –9223372036854775808 to 9223372036854775807. The unsigned range is 0 to 18446744073709551615
FLOAT
    A small (single-precision) floating-point number. Cannot be unsigned
    Ranges are –3.402823466E+38 to –1.175494351E-38, 0 and 1.175494351E-38 to 3.402823466E+38. If the number of Decimals is not set or <= 24 it is a single-precision floating point number
DOUBLE,
DOUBLE PRECISION,
REAL
    A normal-size (double-precision) floating-point number. Cannot be unsigned
    Ranges are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0 and 2.2250738585072014E-308 to 1.7976931348623157E+308. If the number of Decimals is not set or 25 <= Decimals <= 53 stands for a double-precision floating point number
DECIMAL,
NUMERIC
    An unpacked floating-point number. Cannot be unsigned
    Behaves like a CHAR column: “unpacked” means the number is stored as a string, using one character for each digit of the value. The decimal point, and, for negative numbers, the ‘-‘ sign is not counted in Length. If Decimals is 0, values will have no decimal point or fractional part. The maximum range of DECIMAL values is the same as for DOUBLE, but the actual range for a given DECIMAL column may be constrained by the choice of Length and Decimals. If Decimals is left out it’s set to 0. If Length is left out it’s set to 10. Note that in MySQL 3.22 the Length includes the sign and the decimal point
DATE
    A date
    The supported range is ‘1000-01-01’ to ‘9999-12-31’. MySQL displays DATE values in ‘YYYY-MM-DD’ format
DATETIME
    A date and time combination
    The supported range is ‘1000-01-01 00:00:00’ to ‘9999-12-31 23:59:59’. MySQL displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format
TIMESTAMP
    A timestamp
    The range is ‘1970-01-01 00:00:00’ to sometime in the year 2037. MySQL displays TIMESTAMP values in YYYYMMDDHHMMSS, YYMMDDHHMMSS, YYYYMMDD or YYMMDD format, depending on whether M is 14 (or missing), 12, 8 or 6, but allows you to assign values to TIMESTAMP columns using either strings or numbers. A TIMESTAMP column is useful for recording the date and time of an INSERT or UPDATE operation because it is automatically set to the date and time of the most recent operation if you don’t give it a value yourself
TIME
    A time
    The range is ‘-838:59:59’ to ‘838:59:59’. MySQL displays TIME values in ‘HH:MM:SS’ format, but allows you to assign values to TIME columns using either strings or numbers
YEAR
    A year in 2- or 4- digit formats (default is 4-digit)
    The allowable values are 1901 to 2155, and 0000 in the 4 year format and 1970-2069 if you use the 2 digit format (70-69). MySQL displays YEAR values in YYYY format, but allows you to assign values to YEAR columns using either strings or numbers. (The YEAR type is new in MySQL 3.22.)
CHAR
    A fixed-length string that is always right-padded with spaces to the specified length when stored
    The range of Length is 1 to 255 characters. Trailing spaces are removed when the value is retrieved. CHAR values are sorted and compared in case-insensitive fashion according to the default character set unless the BINARY keyword is given
VARCHAR
    A variable-length string. Note: Trailing spaces are removed when the value is stored (this differs from the ANSI SQL specification)
    The range of Length is 1 to 255 characters. VARCHAR values are sorted and compared in case-insensitive fashion unless the BINARY keyword is given
TINYBLOB,
TINYTEXT
   
    A BLOB or TEXT column with a maximum length of 255 (2^8 - 1) characters
BLOB,
TEXT
   
    A BLOB or TEXT column with a maximum length of 65535 (2^16 - 1) characters
MEDIUMBLOB,
MEDIUMTEXT
   
    A BLOB or TEXT column with a maximum length of 16777215 (2^24 - 1) characters
LONGBLOB,
LONGTEXT
   
    A BLOB or TEXT column with a maximum length of 4294967295 (2^32 - 1) characters
ENUM
    An enumeration
    A string object that can have only one value, chosen from the list of values ‘value1’, ‘value2’, ..., or NULL. An ENUM can have a maximum of 65535 distinct values.
SET
    A set
    A string object that can have zero or more values, each of which must be chosen from the list of values ‘value1’, ‘value2’, ... A SET can have a maximum of 64 members

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