SQL support for GRASS.

Supported is a limited set of SQL functions and operators.

ALTER TABLE table ADD [COLUMN] columndef

CREATE TABLE table ( columndefs )

DROP TABLE table

SELECT columns FROM table

SELECT columns FROM table WHERE condition

DELETE FROM table

DELETE FROM table WHERE condition

INSERT INTO table values

INSERT INTO table ( columns ) values

UPDATE table SET assignments

UPDATE table SET assignments WHERE condition

"=" : equal

"<" : smaller than

"<=" : smaller/equal than

">" : larger than

">=" : larger/equal than

"<>" : not equal

"~" : Substring matching

SQL does not support '.' (dots) in table names.

Supported table name characters are only:

[A-Za-z][A-Za-z0-9_]*

A table name must start with a character, not a number.

Brackets are needed, e.g. for

select * from some_table where (3*(some_field - another_field) > 5)

The parser does not know about precedence yet, so the sub-clause has to be in brackets to avoid ambiguity.

Text-string matching requires the text part to be 'single quoted' and multiple queries should be contained in "double quotes". e.g.

d.vect map where="individual='juvenile' and area='beach'"

An error message such as "dbmi: Protocol error" either indicates an invalid column name or an unsupported column type (then the GRASS SQL parser needs to be extended).

DBF column names are limited to 10 characters (DBF API definition)

Display all vector points except for LAMAR valley and extensive trapping:

d.vect trapping_sites_points fcol=black icon=basic/diamond col=white size=13

where="valley <> 'LAMAR' OR (valley = 'LAMAR' AND description = 'extensive trapping')"

Select all attributes from table where str1 column values are not 'No Name':

echo "SELECT * FROM archsites WHERE str1 <> 'No Name'" | db.select

db.execute, db.select, db.tables, d.vect

SQL reference links

Last changed: $Date: 2005/05/10 09:58:07 $

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