SQL QUEL

Introduction to QUEL

  • QUEL stands for Query Language.
  • It is a data definition and data manipulation for INGRES.
  • INGRES stands for Interactive Graphics and Retrieval System.
  • INGRES is a relational database management system developed by Michael Stonebraker.
  • QUEL does not support relational algebraic operations such as intersection, minus or union.
  • It is based on tuple calculus and does not support nested sub queries.

Data Definition in QUEL

Following are the data definition statements used in QUEL,
1. CREATE
2. RANGE
3. INDEX
4. DESTROY
5. MODIFY

StatementsDescriptionSyntax
CREATEIt is used to create tables or relations.CREATE <table-name> <list-of-column-name>
RANGEIt allows to declare a range variable and restricts to assume the values that are rows from the specified table. Row variables are called Range variables in QUEL.RANGE OF <variable-name> IS <relation-name>
INDEXIt is used to specify the name of the secondary index to be built and the columns in the table on which the index is to be created.INDEX ON <table-name> IS <index-name> (column-name [, column-name, ...])
DESTROYIt is used to eliminate a table, index or view.DESTROY name [, name, ...]
MODIFYIt is used to modify the structure of a table. The storage structure supported by INGRES are B-tree, hash, ISAM and heap. The storage structure will be modified from the current one to the one specified in the statement.MODIFY <table-name>
TO <storage-structure>
ON <column-name>
▲