SQL Identifiers

SQL identifiers are names used for different elements within TiDB Cloud Lake, such as tables, views, and databases.

Unquoted & Double-quoted Identifiers

Unquoted identifiers begin with a letter (A-Z, a-z) or underscore (“_”) and may consist of letters, underscores, numbers (0-9), or dollar signs (“$”).

mydatalake
MyDatalake1
My$datalake
_my_datalake

Double-quoted identifiers can include a wide range of characters, such as numbers (0-9), special characters (like period (.), single quote ('), exclamation mark (!), at symbol (@), number sign (#), dollar sign ($), percent sign (%), caret (^), and ampersand (&)), extended ASCII and non-ASCII characters, as well as blank spaces.

"MyDatalake"
"my.datalake"
"my datalake"
"My 'Datalake'"
"1_datalake"
"$Datalake"

Note that using double backticks (``) or double quotes (") is equivalent:

`MyDatalake`
`my.datalake`
`my datalake`
`My 'Datalake'`
`1_datalake`
`$Datalake`

Identifier Casing Rules

TiDB Cloud Lake stores unquoted identifiers by default in lowercase and double-quoted identifiers as they are entered. In other words, TiDB Cloud Lake handles object names, such as databases, tables, and columns, as case-insensitive. If you want TiDB Cloud Lake to handle them as case-sensitive, double-quote them.

This example demonstrates how TiDB Cloud Lake treats the casing of identifiers when creating and listing databases:

-- Create a database named "datalake"
CREATE DATABASE datalake;

-- Attempt to create a database named "Datalake"
CREATE DATABASE Datalake;

>> SQL Error [1105] [HY000]: DatabaseAlreadyExists. Code: 2301, Text = Database 'datalake' already exists.

-- Create a database named "Datalake"
CREATE DATABASE "Datalake";

-- List all databases
SHOW DATABASES;

databases_in_default|
--------------------+
Datalake            |
datalake            |
default             |
information_schema  |
system              |

This example demonstrates how TiDB Cloud Lake handles identifier casing for table and column names, highlighting its case-sensitivity by default and the use of double quotes to differentiate between identifiers with varying casing:

-- Create a table named "datalake"
CREATE TABLE datalake (a INT);
DESC datalake;

Field|Type|Null|Default|Extra|
-----+----+----+-------+-----+
a    |INT |YES |NULL   |     |

-- Attempt to create a table named "Datalake"
CREATE TABLE Datalake (a INT);

>> SQL Error [1105] [HY000]: TableAlreadyExists. Code: 2302, Text = Table 'datalake' already exists.

-- Attempt to create a table with one column named "a" and the other one named "A"
CREATE TABLE "Datalake" (a INT, A INT);

>> SQL Error [1105] [HY000]: BadArguments. Code: 1006, Text = Duplicated column name: a.

-- Double quote the column names
CREATE TABLE "Datalake" ("a" INT, "A" INT);
DESC "Datalake";

Field|Type|Null|Default|Extra|
-----+----+----+-------+-----+
a    |INT |YES |NULL   |     |
A    |INT |YES |NULL   |     |

String Identifiers

In TiDB Cloud Lake, when managing string items like text and dates, it is essential to enclose them within single quotes (') as a standard practice.

INSERT INTO weather VALUES ('San Francisco', 46, 50, 0.25, '1994-11-27');

SELECT 'Datalake';

'datalake'|
----------+
Datalake  |

SELECT "Datalake";

>> SQL Error [1105] [HY000]: SemanticError. Code: 1065, Text = error:
  --> SQL:1:73
  |
1 | /* ApplicationName=DBeaver 23.2.0 - SQLEditor <Script-12.sql> */ SELECT "Datalake"
  |                                                                         ^^^^^^^^^^ column Datalake doesn't exist, do you mean 'Datalake'?

By default, TiDB Cloud Lake SQL dialect is PostgreSQL:

SHOW SETTINGS LIKE '%sql_dialect%';

name       |value     |default   |level  |description                                                                      |type  |
-----------+----------+----------+-------+---------------------------------------------------------------------------------+------+
sql_dialect|PostgreSQL|PostgreSQL|SESSION|Sets the SQL dialect. Available values include "PostgreSQL", "MySQL", and "Hive".|String|

You can change it to MySQL to enable double quotes ("):

SET sql_dialect='MySQL';

SELECT "demo";
+--------+
| 'demo' |
+--------+
| demo   |
+--------+