STRING

The STRING data type stores a string of Unicode characters.

Note:

STRING is not a data type supported by PostgreSQL. For PostgreSQL compatibility, CockroachDB supports additional aliases and STRING-related types.

Aliases

CockroachDB supports the following alias for STRING:

  • TEXT

For PostgreSQL compatibility, CockroachDB supports the following STRING-related types and their aliases:

  • VARCHAR (and alias CHARACTER VARYING)
  • CHAR (and alias CHARACTER)

These types are functionality identical to STRING.

Length

To limit the length of a string column, use STRING(n), where n is the maximum number of Unicode code points (normally thought of as "characters") allowed. This applies to all related types as well (e.g., to limit the length of a VARCHAR type, use VARCHAR(n)).

When inserting a STRING value or a STRING-related-type value:

  • If the value is cast with a length limit (e.g., CAST('hello world' AS STRING(5))), CockroachDB truncates to the limit. This applies to STRING(n) and all related types.
  • If the value exceeds the column's length limit, CockroachDB returns an error. This applies to STRING(n) and all related types.
  • For STRING(n) and VARCHAR(n)/CHARACTER VARYING(n) types, if the value is under the column's length limit, CockroachDB does not add space padding to the end of the value.
  • For CHAR(n)/CHARACTER(n) types, if the value is under the column's length limit, CockroachDB adds space padding from the end of the value to the length limit.

    Type Length
    CHARACTER, CHARACTER(n), CHAR, CHAR(n) Fixed-length
    CHARACTER VARYING(n), VARCHAR(n), STRING(n) Variable-length, with a limit
    TEXT, VARCHAR, CHARACTER VARYING, STRING Variable-length, with no limit

Syntax

A value of type STRING can be expressed using a variety of formats. See string literals for more details.

When printing out a STRING value in the SQL shell, the shell uses the simple SQL string literal format if the value doesn't contain special character, or the escaped format otherwise.

Collations

STRING values accept collations, which lets you sort strings according to language- and country-specific rules.

Size

The size of a STRING value is variable, but it's recommended to keep values under 64 kilobytes to ensure performance. Above that threshold, write amplification and other considerations may cause significant performance degradation.

Examples

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> CREATE TABLE strings (a STRING PRIMARY KEY, b STRING(4), c TEXT);
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> SHOW COLUMNS FROM strings;
  column_name | data_type | is_nullable | column_default | generation_expression |   indices   | is_hidden
+-------------+-----------+-------------+----------------+-----------------------+-------------+-----------+
  a           | STRING    |    false    | NULL           |                       | {"primary"} |   false
  b           | STRING(4) |    true     | NULL           |                       | {}          |   false
  c           | STRING    |    true     | NULL           |                       | {}          |   false
(3 rows)
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> INSERT INTO strings VALUES ('a1b2c3d4', 'e5f6', 'g7h8i9');
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> SELECT * FROM strings;
     a     |  b   |   c
+----------+------+--------+
  a1b2c3d4 | e5f6 | g7h8i9
(1 row)
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> CREATE TABLE aliases (a STRING PRIMARY KEY, b VARCHAR, c CHAR);
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> SHOW COLUMNS FROM aliases;
  column_name | data_type | is_nullable | column_default | generation_expression |   indices   | is_hidden
+-------------+-----------+-------------+----------------+-----------------------+-------------+-----------+
  a           | STRING    |    false    | NULL           |                       | {"primary"} |   false
  b           | VARCHAR   |    true     | NULL           |                       | {}          |   false
  c           | CHAR      |    true     | NULL           |                       | {}          |   false
(3 rows)

Supported casting and conversion

STRING values can be cast to any of the following data types:

Type Details
ARRAY Requires supported ARRAY string format, e.g., '{1,2,3}'.
Note that string literals can be implicitly cast to any supported ARRAY data type except BYTES, ENUM, JSONB, SERIAL, and the spatial data types Box2D, GEOGRAPHY, and GEOMETRY.
BIT Requires supported BIT string format, e.g., '101001'.
BOOL Requires supported BOOL string format, e.g., 'true'.
BYTES For more details, see here.
DATE Requires supported DATE string format, e.g., '2016-01-25'.
DECIMAL Requires supported DECIMAL string format, e.g., '1.1'.
FLOAT Requires supported FLOAT string format, e.g., '1.1'.
INET Requires supported INET string format, e.g, '192.168.0.1'.
INT Requires supported INT string format, e.g., '10'.
INTERVAL Requires supported INTERVAL string format, e.g., '1h2m3s4ms5us6ns'.
TIME Requires supported TIME string format, e.g., '01:22:12' (microsecond precision).
TIMESTAMP Requires supported TIMESTAMP string format, e.g., '2016-01-25 10:10:10.555555'.

STRING vs. BYTES

While both STRING and BYTES can appear to have similar behavior in many situations, one should understand their nuance before casting one into the other.

STRING treats all of its data as characters, or more specifically, Unicode code points. BYTES treats all of its data as a byte string. This difference in implementation can lead to dramatically different behavior. For example, let's take a complex Unicode character such as ☃ (the snowman emoji):

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> SELECT length('☃'::string);
  length
+--------+
       1
> SELECT length('☃'::bytes);
  length
+--------+
       3

In this case, LENGTH(string) measures the number of Unicode code points present in the string, whereas LENGTH(bytes) measures the number of bytes required to store that value. Each character (or Unicode code point) can be encoded using multiple bytes, hence the difference in output between the two.

Translating literals to STRING vs. BYTES

A literal entered through a SQL client will be translated into a different value based on the type:

  • BYTES give a special meaning to the pair \x at the beginning, and translates the rest by substituting pairs of hexadecimal digits to a single byte. For example, \xff is equivalent to a single byte with the value of 255. For more information, see SQL Constants: String literals with character escapes.
  • STRING does not give a special meaning to \x, so all characters are treated as distinct Unicode code points. For example, \xff is treated as a STRING with length 4 (\, x, f, and f).

Concatenating STRING values with values of other types

STRING values can be concatenated with any non-ARRAY, non-NULL type, resulting in a STRING value.

For example:

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> SELECT 1 || 'item';
  ?column?
------------
  1item
(1 row)
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> SELECT true || 'item';
  ?column?
------------
  titem
(1 row)

Concatenating a STRING value with a NULL value results in a NULL value.

For example:

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> SELECT NULL || 'item';
  ?column?
------------
  NULL
(1 row)

See also

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