Dimensioni dei Tipi di Dati

Le seguenti tabelle indicano approssimativamente lo spazio occupato da ogni tipo di dato.

Tipi numerici

TipoSpazio occupato
TINYINT1 byte
SMALLINT2 byte
MEDIUMINT3 byte
INT4 byte
BIGINT8 byte
FLOAT(p)4 byte se p <= 24, altrimenti 8 byte
DOUBLE8 byte
DECIMALVedi tabella sotto
BIT(M)(M+7)/8 byte

Decimali

I Decimali sono registrati in formato binario, con la parte intera e quella frazionale registrate separatamente. Per ogni nove cifre occorrono 4 byte, seguiti da un certo numero di byte per ciò che rimane, come segue:

Cifre rimanentiSpazio occupato
00 byte
11 byte
21 byte
32 byte
42 byte
53 byte
63 byte
74 byte
84 byte

String data types

In the descriptions below, M is the declared column length (in characters or in bytes), while len is the actual length in bytes of the value.

Data TypeStorage Requirement
ENUM1 byte for up to 255 enum values, 2 bytes for 256 to 65,535 enum values
CHAR(M)M × w bytes, where w is the number of bytes required for the maximum-length character in the character set
BINARY(M)M bytes
VARCHAR(M), VARBINARY(M)len + 1 bytes if column is 0 – 255 bytes, len + 2 bytes if column may require more than 255 bytes
TINYBLOB, TINYTEXTlen + 1 bytes
BLOB, TEXTlen + 2 bytes
MEDIUMBLOB, MEDIUMTEXTlen + 3 bytes
LONGBLOB, LONGTEXTlen + 4 bytes
SETGiven M members of the set, (M+7)/8 bytes, rounded up to 1, 2, 3, 4, or 8 bytes

In some character sets, not all characters use the same number of bytes. utf8 encodes characters with one to three bytes per character, while utf8mb4 requires one to four bytes per character.

Date and time data types

Data TypeStorage Requirement
DATE3 bytes
TIME3 bytes
DATETIME8 bytes
TIMESTAMP4 bytes
YEAR1 byte

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