Analysis of the data types MySQL
MySQL There are several types of data may be limited type of "length", there CHAR (Length), VARCHAR (Length), TINYINT (Length), SMALLINT (Length), MEDIUMINT (Length), INT (Length), BIGINT (Length), FLOAT (Length, Decimals), DOUBLE (Length, Decimals) and DECIMAL (Length, Decimals).
However, the length of these data types, not all referring to the data size. Specifically, that is to:
(1) the length of CHAR, VARCAHR is the length of a character, for example, CHAR [3] can only put the string "123", if the insertion data "1234", taken from the high, to "123" . VARCAHR empathy.
(2) the length TINYINT, SMALLINT, MEDIUMINT, INT and BIGINT, in fact, independent of the size of the data and! Length refers to the display width, for example: int (3) is shown as three digital memory 001 is shown as a
As can be seen, the display width of 3 id, the left 0s insufficient, as it is longer than the data output. ZEROFILL If not, see if the display width, without leading zeros.
(3) the length of FLOAT, DOUBLE and DECIMAL refers to the total number of bits (including after the decimal point), e.g. DECIMAL (4,1) refers to the total number of digits is 4, one after the decimal point, if the insert 1234, the query data is 999.9. Follows
Appendix common MySQL data types (reserved memo)
| Types of |
Size |
Description |
| CAHR(Length) |
Length byte |
Fixed-length field, a length of 0 to 255 characters |
| VARCHAR(Length) |
String String length + length byte + 2 bytes or |
Variable-length field, a length of from 0 to 65,535 characters. |
| TINYTEXT |
String length + 1 byte |
String with a maximum length of 255 characters |
| TEXT |
String length byte + 2 |
String with a maximum length of 65 characters 535 |
| MEDIUMINT |
String length byte + 3 |
String with a maximum length of 16 777 215 characters |
| LONGTEXT |
String length of 4 bytes |
String with a maximum length of 4,294,967,295 characters |
| TINYINT(Length) |
1 byte |
Range: -128 to 127, or 0 to 255 (unsigned) |
| SMALLINT(Length) |
2 bytes |
Range: -32 768 to 32 767 or 65 535 0 ~ (unsigned) |
| MEDIUMINT(Length) |
3 bytes |
Range: -8388608 8388607 ~ or ~ 0 16777215 (unsigned) |
| INT(Length) |
4 bytes |
Range: ~ -2 147 483 648 2 147 483 647, or 0 to 4,294,967,295 (unsigned) |
| BIGINT(Length) |
8 bytes |
Range: -9,223,372,036,854,775,808 ~ 9,223,372,036,854,775,807, or 0-18 446,744,073,709,551 615 (unsigned) |
| FLOAT(Length, Decimals) |
4 bytes |
Having a smaller number of floating point |
| DOUBLE(Length, Decimals) |
8 bytes |
Having a large number of floating point |
| DECIMAL(Length, Decimals) |
Length + 1 byte or bytes Length + 2 |
DOUBLE stored as a string, allowing for a fixed decimal point |
| DATE |
3 bytes |
Using YYYY-MM-DD format |
| DATETIME |
8 bytes |
Using YYYY-MM-DD HH: MM: SS format |
| TIMESTAMP |
4 bytes |
Using YYYYMMDDHHMMSS format; terminates in an acceptable range 2037 |
| TIME |
3 bytes |
Using HH: MM: SS format |
| ENUM |
1 or 2 bytes |
Enumeration (enumeration) shorthand, which means that each column can have one of several possible values |
| SET |
3, 4 or 8 bytes |
And ENUM same, but each column can have multiple possible values |
以上 转自 https://blog.csdn.net/DayDreamingBoy/article/details/6310907
Mysql文字长度限制TEXT、TINYTEXT、MEDIUMTEXT、LONGTEXT
有4种TEXT类型：TINYTEXT、TEXT、MEDIUMTEXT和LONGTEXT。这些对应4种BLOB类型，有相同的最大长度和存储需求。
BLOB是一个二进制大对象，可以容纳可变数量的数据。有4种BLOB类型：TINYBLOB、BLOB、MEDIUMBLOB和LONGBLOB。它们只是可容纳值的最大长度不同。
tinytext, tinyBlob: 最大长度255个字元(2^8-1)
text, Blob: 最大长度65535个字元(2^16-1)
mediumtext, mediumBlob: 最大长度 16777215 个字元(2^24-1)
longtext, longBlob: 最大长度4294967295个字元 (2^32-1)