A record selection expression is used to select a record in the
  database.  It can be used in a FETCH or FIND statement.  The record
  thus selected becomes the current record of the run unit upon which
  subsequent statements may operate when accessing the database.

1 - 1format_database_key_identifier_access

  This format selects a record by a database key value held by the
  Database Control System (DBCS) in a currency indicator or a keeplist
  entry.

  Format 1 - Database Key Identifier Access

   database-key-identifier

 1.1 - database-key-identifier

  identifies a record according to the rules of Database Key
  Identifiers.

2 - 2format_set_owner_access

  This format selects the record that owns a set.

  Format 2 - Set Owner Access

   OWNER WITHIN set-name

 2.1 - set-name

  is a subschema set name.  The Database Control System (DBCS) uses
  the currency indicator for set-name to choose the owner record of
  that set occurrence.  A database exception condition occurs if
  set-name is a singular set (DB-CONDITION is set to DBM$_SINGTYP) or
  if the currency indicator for the set type is null (DB-CONDITION is
  set to DBM$_CSTYP_NULL).

3 - 3format_record_search_access

  This format selects a record by its position within a collection of
  records and optionally by its record type and contents.

  Format 3 - Record Search Access

  { FIRST                }
  { LAST                 }
  { NEXT                 }
  { PRIOR                }
  { ANY                  }
  { DUPLICATE            }
  { [ RELATIVE ] int-exp }

    [record-name] [ WITHIN { realm-name } ] [ USING { rec-key } ... ]
                  [        { set-name   } ] [ WHERE { bool-expres } ]

 3.1 - int-exp

  is an integer or arithmetic expression resulting in a longword
  integer value.  It cannot be zero.

 3.2 - realm-name

  is a subschema realm name.

 3.3 - record-name

  is a subschema record name.

 3.4 - set-name

  is a subschema set name.

 3.5 - rec-key

  is a key data item within the subschema record occurrence.  The
  same rec-key can appear only once in a given USING phrase.

 3.6 - bool-expres

  is a conditional expression that involves data items of the object
  record.  It is used to specify additional requirements of a
  qualifying record.

    bool-expres:
      { bool-alt [ OR bool-alt ] ... }
    bool-alt:
      { simp-bool-rel [ AND simp-bool-rel ] ... }
    simp-bool-rel:
      { bool-condit     }
      { NOT bool-expres }
    bool-condit:
      {          {         {[ NOT ] EQUAL TO          } }         }
      {          {         {[ NOT ] =                 } }         }
      {          {         {[ NOT ] LESS THAN         } }         }
      {          { IS      {[ NOT ] <                 } }         }
      {          {         {[ NOT ] GREATER THAN      } }         }
      {          {         {[ NOT ] >                 } }         }
      { { id  }  {         { GREATER THAN OR EQUAL TO } } { id  } }
      { { lit }  {         { >=                       } } { lit } }
      {          {         { LESS THAN OR EQUAL TO    } }         }
      {          {         { <=                       } }         }
      {          { DOES    {[ NOT ] CONTAIN           } }         }
      {          {         {[ NOT ] CONTAINS          } }         }
      {          {         {[ NOT ] MATCH             } }         }
      {          {         {[ NOT ] MATCHES           } }         }

 3. 6.1 - bool-alt

  is one or more sub-expressions (simp-bool-rel).  Pairs of
  sub-expressions are joined by the logical operator AND.

 3. 6.2 - simp-bool-rel

  is a simple-condition (bool-condit), an expression, or the
  negation of either.

 3. 6.3 - bool-condit

  a simple-condition is a relation involving two operands joined by
  a relational operator.  At least one operand in each relation
  must be an item in the record being found or fetched.

4 - 4format_database_key_access

  This format selects the record that is referred to by the database
  key value contained in the special register DB-KEY.

  Format 4 - Database Key Access

    DBKEY