About ACEDB Queries

Other very useful documents on ACEDB query language are:

• ACEDB Online Help (July 1994)
• Searching an ACeDB database, by Dave Matthews and Suzanna Lewis (May 1995)
• More ACEDB Query Language Examples, by JD Barnett (December 1995)

Examples

So how do you find out the class and tag names for the database you are interested in? All class and tag names are listed in the "model" or structure of the database. One of the first ACEDB queries you should do is list the database model (see the Examples). This will give you the information necessary to construct queries for the data you want to see.

It is important to list the model of every database you want to query because not all databases use the same model. Each organism has developed a database structure to suit their individual needs, although many class names and constructs are similar. This is the reason why some of the examples may work in one database but not in another.

Query construction

Parentheses of all sorts "([{" can be used freely, but must be matched.

Words or strings are matched to a tag or treated as text. They must be put in "double quotes" if they include spaces or any operator &, |, ^, <, >, =, (, ), [, ], {, }. Wild cards (* for multiple characters or ? for a single character) can be used in words.

Good learning tools for those wishing to master ACEDB query syntax are Query by Example and Query Builder. Both return a formal query string, along with the query results when a query is submitted.

Query commands

find class pattern

finds all objects belonging to class and matching patternin the database

follow tag

from the currently selected objects, returns all objects that also have tag

tag

tests the currently selected objects for the existence of tag. Note, this command can only be used after another query, not as an initial query.

grep pattern

finds all database objects that match pattern. Note, this often returns too many objects to be useful.

HERE | NEXT

tests the value under the pointer (HERE) or on the next value to the right (NEXT). Use this when there are two or more fields associated with a tag.

Query operators, in order of increasing precedence

argument1 OR argument2

evaluates to TRUE if at least one of argument1 or argument2 evaluate to true (alternative: |)

argument1 XOR argument2

evaluates to TRUE if either argument1 or argument2 evaluates to true, but not both (alternative: ^)

argument1 AND argument2

evaluates to TRUE if both argument1 and argument2 evaluates to true (alternative: %)

NOT argument

negates the result of the argument (alternative: !)

tag #

jumps into constructed types following tag

argument < pattern

less than, to compare numbers (alternative: LT)

argument <= pattern

less than or equal to, to compare numbers (alternative: LE)

argument > pattern

greater than, to compare numbers (alternative: GT)

argument >= pattern

greater than or equal to, to compare numbers (alternative: GE)

argument = pattern

equal, to compare numbers or match the pattern, i.e., a word with wild cards * or ?

argument != pattern

not equal, to compare numbers or match the pattern, i.e., a word with wild cards * or ? (alternative: NEQ)

COUNT tag

counts the number of data items following the tag

Advanced Queries -- Subfields

A common subfield query is to locate loci on a genetic map using the class Locus and tag Map. The information is stored in a sequence of subfields as in this sample:

  Locus   Location Map    Hordeum-Graner2-7H   Position    141
    ^             ^               ^               ^         ^
  class          tag            value            tag      value

find Locus Map = *7h AND NEXT AND NEXT > 140 AND HERE < 150

The first AND NEXT moves off the Map value (*7h), the second AND NEXT skips over the Position tag and evaluates the Position value, and the AND HERE stays on the Position value and evaluates it again.