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 to the following list (which is part of the DDL required to build the table)?

TABLE: ARTICLES
ID INTEGER NOT NULL
PRINTED SMALLINT DEFAULT 0
ACADEMIC SMALLINT
RELEVANCE SMALLINT
SOURCE VARCHAR(64) CHARACTER SET WIN1251 COLLATE WIN1251
NAME VARCHAR(128) CHARACTER SET WIN1251 COLLATE WIN1251
FILENAME VARCHAR(128) CHARACTER SET WIN1251 COLLATE WIN1251
NOTES VARCHAR(2048) CHARACTER SET WIN1251 COLLATE WIN1251

Answer 1

This is incomplete (because I've never used Firebird array data types) and not much tested but perhaps it will give you a good starting point:

SELECT
  RF.RDB$FIELD_NAME FIELD_NAME,
  CASE F.RDB$FIELD_TYPE
    WHEN 7 THEN
      CASE F.RDB$FIELD_SUB_TYPE
        WHEN 0 THEN 'SMALLINT'
        WHEN 1 THEN 'NUMERIC(' || F.RDB$FIELD_PRECISION || ', ' || (-F.RDB$FIELD_SCALE) || ')'
        WHEN 2 THEN 'DECIMAL'
      END
    WHEN 8 THEN
      CASE F.RDB$FIELD_SUB_TYPE
        WHEN 0 THEN 'INTEGER'
        WHEN 1 THEN 'NUMERIC('  || F.RDB$FIELD_PRECISION || ', ' || (-F.RDB$FIELD_SCALE) || ')'
        WHEN 2 THEN 'DECIMAL'
      END
    WHEN 9 THEN 'QUAD'
    WHEN 10 THEN 'FLOAT'
    WHEN 12 THEN 'DATE'
    WHEN 13 THEN 'TIME'
    WHEN 14 THEN 'CHAR(' || (TRUNC(F.RDB$FIELD_LENGTH / CH.RDB$BYTES_PER_CHARACTER)) || ') '
    WHEN 16 THEN
      CASE F.RDB$FIELD_SUB_TYPE
        WHEN 0 THEN 'BIGINT'
        WHEN 1 THEN 'NUMERIC(' || F.RDB$FIELD_PRECISION || ', ' || (-F.RDB$FIELD_SCALE) || ')'
        WHEN 2 THEN 'DECIMAL'
      END
    WHEN 27 THEN 'DOUBLE'
    WHEN 35 THEN 'TIMESTAMP'
    WHEN 37 THEN 'VARCHAR(' || (TRUNC(F.RDB$FIELD_LENGTH / CH.RDB$BYTES_PER_CHARACTER)) || ')'
    WHEN 40 THEN 'CSTRING' || (TRUNC(F.RDB$FIELD_LENGTH / CH.RDB$BYTES_PER_CHARACTER)) || ')'
    WHEN 45 THEN 'BLOB_ID'
    WHEN 261 THEN 'BLOB SUB_TYPE ' || F.RDB$FIELD_SUB_TYPE
    ELSE 'RDB$FIELD_TYPE: ' || F.RDB$FIELD_TYPE || '?'
  END FIELD_TYPE,
  IIF(COALESCE(RF.RDB$NULL_FLAG, 0) = 0, NULL, 'NOT NULL') FIELD_NULL,
  CH.RDB$CHARACTER_SET_NAME FIELD_CHARSET,
  DCO.RDB$COLLATION_NAME FIELD_COLLATION,
  COALESCE(RF.RDB$DEFAULT_SOURCE, F.RDB$DEFAULT_SOURCE) FIELD_DEFAULT,
  F.RDB$VALIDATION_SOURCE FIELD_CHECK,
  RF.RDB$DESCRIPTION FIELD_DESCRIPTION
FROM RDB$RELATION_FIELDS RF
JOIN RDB$FIELDS F ON (F.RDB$FIELD_NAME = RF.RDB$FIELD_SOURCE)
LEFT OUTER JOIN RDB$CHARACTER_SETS CH ON (CH.RDB$CHARACTER_SET_ID = F.RDB$CHARACTER_SET_ID)
LEFT OUTER JOIN RDB$COLLATIONS DCO ON ((DCO.RDB$COLLATION_ID = F.RDB$COLLATION_ID) AND (DCO.RDB$CHARACTER_SET_ID = F.RDB$CHARACTER_SET_ID))
WHERE (RF.RDB$RELATION_NAME = :TABLE_NAME) AND (COALESCE(RF.RDB$SYSTEM_FLAG, 0) = 0)
ORDER BY RF.RDB$FIELD_POSITION;