How can I get the table description (fields and types) from Firebird with dbExpress

Question

I have written a tool for displaying database structures using the GetTableNames and GetFieldNames methods of TSQLConnection. How can I get the types of each field name similar

Answer 1

Use direct access to RDB$ tables. For example:

SELECT * FROM rdb$relations

will give you a list of all tables in a database.

SELECT
  *
FROM
  rdb$relation_fields rf JOIN rdb$fields f
    ON f.rdb$field_name = rf.rdb$field_source
WHERE
  rf.rdb$relation_name = :RN

will result in a list of all fields of given table with information of field type. Param RN is a name of the table.

Using information from RDB$tables one can easily construct DDL statement. The query below gives you a hint how to do it:

SELECT
  TRIM(rf.rdb$field_name) || ' ' ||
  IIF(rdb$field_source LIKE 'RDB$%',
  DECODE(f.rdb$field_type, 
    8,  'INTEGER', 
    12, 'DATE', 
    37, 'VARCHAR', 
    14, 'CHAR', 
    7,  'SMALLINT'),
  TRIM(rdb$field_source)) ||
  IIF((rdb$field_source LIKE 'RDB$%') AND (f.rdb$field_type IN (37, 14)),
    '(' || f.rdb$field_length || ')',
    '') ||
  IIF((f.rdb$null_flag = 1) OR (rf.rdb$null_flag = 1), 
    ' NOT NULL', '')
FROM
  rdb$relation_fields rf JOIN rdb$fields f
    ON f.rdb$field_name = rf.rdb$field_source
WHERE
  rf.rdb$relation_name = ''