How different is QUEL from SQL?
VERY different, although in embedded applications, where the two DMLs are used only for the basic operations of fetching, updating and inserting, the differences are not very apparent. A few of the important differences in embedded applications are: • In EQUEL the INGRES identifiers are flagged (viz #part_no = part_no), while ESQL the host-language identifiers are flagged (viz part_no = :part_no). • QUEL allows range variables (analogous to SQL correlated table names) to remain defined between statements. A range variable declaration need not appear in the source code anywhere near the reference to the range variable. • The EQUEL `APPEND’ statement (analogous to SQL `INSERT’) insists that column be identified by name–columns cannot be addressed by position. • EQUEL allows the WHERE clause to be defined dynamically, without recourse to a “dynamic” EQUEL. As well, some of the other difference that apply to both the embedded and non-embedded version of QUEL, but which are perhaps of grea
