MySQL is a relational database management systems, relational database stores data in separate tables rather than putting all the data in a large warehouse, thus increasing the speed and improved flexibility. MySQL SQL language used is the most common standardized language used to access databases. MySQL software uses a dual licensing policy, divided communities and commercial versions, because of its small size, high speed, low cost of ownership, especially open source this feature, the development of small and medium websites have chosen MySQL as the database website
With other languages, also has its own data type, here to tell you about mysql commonly used data types:
Integer type byte range (signed) range (unsigned) use
FLOAT 4 bytes (-3.402 823 466 E + 38,1.175 494 351 E-38), 0, (1.175 494 351 E-38,3.402 823 466 351 E + 38) 0, (1.175 494 351 E-38,3.402 823 466 E + 38) single-precision floating-point value
DOUBLE 8 bytes (1.797 693 134 862 315 7 E + 308,2.225 073 858 507 201 4 E-308), 0, (2.225 073 858 507 201 4 E-308,1.797 693 134 862 315 7 E + 308) 0 , (2.225 073 858 507 201 4 E-308,1.797 693 134 862 315 7 E + 308) double precision floating point value
DECIMAL of DECIMAL (M, D), if M> D, the value is a small value of M + 2 or D + 2 depends on the value of M depends on M and D and D
Optional integer attribute column
M: width (filled with 0 when it makes sense)
unsigned: unsigned type (non-negative)
zerofill: 0 filler, (unsigned default)
Date and Time Types
DATE 3 bytes
DATETIME 8 bytes
TIMESTAMP 4 bytes
TIME 3 bytes
YEAR 1 byte, may also exist in 0000
String type
Special type NULL
NULL is not fake, not real, but "empty"
Any operator determines character encountered NULL, NULL had
NULL judgment can only use is null, is not null
NULL affect query speed, generally avoid the value is NULL
By use of each data type, range, etc. represents a summary of understanding, then according to the selected storage engine to determine how to select the appropriate data type. In exchange for higher performance with a smaller database storage costs.