Naming Conventions and Limitations

Naming Rules

1. Legal characters: English letters, numbers, and underscores.
2. Names may start with English letters or underscores, but cannot start with numbers.
3. Case insensitive.
4. Cannot be a reserved keyword.
5. Rules for escaped table (column) names: To support more forms of table (column) names, TDengine introduces a new escape character ". After using the escape character:
   • Case uniformity is no longer applied to the content within escape characters, allowing the preservation of case sensitivity in user-specified table names. For example, `aBc` and `abc` are considered different table (column) names, while abc and aBc are treated as the same table (column) name.
   • Table (column) names can include characters other than letters, numbers, and underscores, such as `abc@TD`, but escaped names still cannot contain .; otherwise, the error The table name cannot contain '.' will be prompted.
   • Names can start with numbers, such as `1970`.
   • Names can be the same as reserved keywords, such as `select`.

Password Legal Character Set

[a-zA-Z0-9!?$%^&*()_–+={[}]:;@~#|<,>.?/]

This excludes ‘“`\ (single quotes, double quotes, apostrophes, backslashes, spaces).

General Restrictions

• Maximum length of database name: 64 bytes
• Maximum length of table name: 192 bytes, excluding database prefix and separator
• Maximum length of each data row: 48KB (64KB starting from version 3.0.5.0) (Note: Each BINARY/NCHAR type column in a data row will also occupy an additional 2 bytes of storage space.)
• Maximum length of column name: 64 bytes
• Maximum allowed columns: 4096, with a minimum of 2 columns, the first column must be a timestamp.
• Maximum length of tag name: 64 bytes
• Maximum allowed tags: 128, with at least 1 tag, the total length of tag values in a table cannot exceed 16KB.
• Maximum length of SQL statements: 1,048,576 characters
• For SELECT statement results, a maximum of 4096 columns are allowed (function calls in the statement may also occupy some column space); if exceeded, fewer return data columns must be explicitly specified to avoid execution errors.
• The number of databases, supertables, and tables is not restricted by the system, only limited by system resources.
• The number of database replicas can only be set to 1 or 3.
• Maximum length of username: 23 bytes
• Maximum length of user password: 31 bytes
• Total number of data rows depends on available resources.
• Maximum number of virtual nodes per single database: 1024