String data type

The string data type is the most commonly used data type. Thanks to this, both text and various binary data (for example, pictures) are stored in the database.

In MySQL, it is represented by the following types:

CHAR and VARCHAR

Type	Description	Range of characters
CHAR(X)	Contains non-binary strings. The length is fixed, you specify it when declaring. If the length of the string is less than the specified one, it is padded with right spaces to the specified length.	The length can be any in the range from 0 to 255
VARCHAR(X)	Contains non-binary strings. The length of the lines is dynamic.	The length can be any in the range from 0 to 65,535

BINARY and VARBINARY

The BINARY and VARBINARY data types are similar to VARCHAR and CHAR except that they store binary strings.

Type	Description	Range of characters
BINARY(X)	Contains binary strings. The length is fixed, you specify it when declaring.	The length can be any in the range from 0 to 255
VARBINARY(X)	Contains binary strings. The length of the lines is dynamic.	The length can be any in the range from 0 to 65,535

BLOB and TEXT

BLOB is used to store large binary data such as pictures. TEXT is also for storing big data, but textual content.

The difference between them is that the sorts and comparisons of stored data for BLOB are case sensitive and not case sensitive in TEXT fields.

Type	Description	Range of characters
BLOB	Contains binary strings.	Maximum length 65,535
TEXT	Contains text lines.	Maximum length 65,535

BLOB and TEXT have additional subtypes that differ in the maximum data size that can be stored in them.

Type	Range of characters
TINYBLOB	Maximum length 255
MEDIUMBLOB	Maximum length 16,777,215
LONGBLOB	Maximum length 4,294,967,295
TINYTEXT	Maximum length 255
MEDIUMTEXT	Maximum length 16,777,215
LONGTEXT	Maximum length 4,294,967,295

In PostgreSQL, it is represented by the following types:

CHARACTER and VARCHAR

Type	Description	Range of characters
CHAR(n)	Contains text strings of fixed length. Padded with spaces to specified length.	Length can be any in the range from 1 to 10,485,760
VARCHAR(n)	Contains text strings of variable length with limitation.	Length can be any in the range from 1 to 10,485,760
TEXT	Contains text strings of unlimited variable length.	Practically unlimited length (up to 1 GB)

It's important to note that in PostgreSQL, the TEXT type is preferable to use instead of VARCHAR without length limitation, as they have the same performance.