diff --git a/general/development/tools/xmldb.md b/general/development/tools/xmldb.md index 22ba8212c7..f91249bd1e 100644 --- a/general/development/tools/xmldb.md +++ b/general/development/tools/xmldb.md @@ -74,21 +74,39 @@ Choose the 'View PHP Code' option and then copy and paste the generated code. Apart from the [Database Structures guidelines](https://docs.moodle.org/dev/Database), some more conventions should be followed: -1. About names: - 1. All lowercase names (tables, indexes, keys and fields). - 1. Table names and field names must use only a-z, 0-9 and _ chars. Max 28 characters. - 1. Key and index names under the XMLDB Files must be formed by concatenating the name of the fields present in the key/index with the '"-" (minus) character. - 1. Primary key always must be named "primary" (this is one exception to the previous convention). - 1. It's highly recommended to avoid [reserved words](https://docs.moodle.org/dev/XMLDB_reserved_words) completely. We know we have some of them now but they should be completely out for next releases. -1. About NULLS - 1. Avoid to create all the fields as NOT NULL with the *silly* default value `*` (empty string). The underlying code used to create tables will handle it properly but the XMLDB structure must be REAL. Read more in the [Problems Page](https://docs.moodle.org/dev/XMLDB_Problems#NOT_NULL_fields_using_a_DEFAULT_*_clause). -1. About FOREIGN KEYS - 1. Under the tables of every XMLDB file, you must define the existing **Foreign Keys** (FK) properly. This will allow everybody to know a bit better the structure, allow to evolve to a better constrained system in the future and will provide the underlying code with the needed info to create the proper indexes. - 1. Note that, if you define any field combination as FK you won't have to create any index on that fields, the code will do it automatically! - 1. Respect Convention 1.3 -1. About UNIQUE KEYS - 1. Declare any fields as UNIQUE KEY (UK) only if they are going to be used as target for one FK. Create unique indexes instead. - 1. Respect Convention 1.3 +
    +
  1. + About names: +
      +
    1. All lowercase names (tables, indexes, keys and fields).
      2. +
    2. Table names and field names must use only a-z, 0-9 and _ chars. Max 28 characters.
      3. +
    3. Key and index names under the XMLDB Files must be formed by concatenating the name of the fields present in the key/index with the '"-" (minus) character.
      4. +
    4. Primary key always must be named "primary" (this is one exception to the previous convention).
      5. +
    5. It's highly recommended to avoid reserved words completely. We know we have some of them now but they should be completely out for next releases.
      6. +
    +
    2. +
  2. + About NULLS +
      +
    1. Avoid to create all the fields as NOT NULL with the silly default value '' (empty string). The underlying code used to create tables will handle it properly but the XMLDB structure must be REAL. Read more in the Problems Page.
      2. +
    +
    3. +
  3. + About FOREIGN KEYS +
      +
    1. Under the tables of every XMLDB file, you must define the existing Foreign Keys (FK) properly. This will allow everybody to know a bit better the structure, allow to evolve to a better constrained system in the future and will provide the underlying code with the needed info to create the proper indexes.
      2. +
    2. Note that, if you define any field combination as FK you won't have to create any index on that fields, the code will do it automatically!
      3. +
    3. Respect Convention 1.3
      4. +
    +
    4. +
  4. + About UNIQUE KEYS +
      +
    1. Declare any fields as UNIQUE KEY (UK) only if they are going to be used as target for one FK. Create unique indexes instead.
      2. +
    2. Respect Convention 1.3
      3. +
    +
    5. +
## See also