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  • How do I use Django to insert a Geometry Field into the database?

    - by alex
    class LocationLog(models.Model): user = models.ForeignKey(User) utm = models.GeometryField(spatial_index=True) This is my database model. I would like to insert a row. I want to insert a circle at point -55, 333. With a radius of 10. How can I put this circle into the geometry field? Of course, then I would want to check which circles overlap a given circle. (my select statement)

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  • What are the Options for Storing Hierarchical Data in a Relational Database?

    - by orangepips
    Good Overviews One more Nested Intervals vs. Adjacency List comparison: the best comparison of Adjacency List, Materialized Path, Nested Set and Nested Interval I've found. Models for hierarchical data: slides with good explanations of tradeoffs and example usage Representing hierarchies in MySQL: very good overview of Nested Set in particular Hierarchical data in RDBMSs: most comprehensive and well organized set of links I've seen, but not much in the way on explanation Options Ones I am aware of and general features: Adjacency List: Columns: ID, ParentID Easy to implement. Cheap node moves, inserts, and deletes. Expensive to find level (can store as a computed column), ancestry & descendants (Bridge Hierarchy combined with level column can solve), path (Lineage Column can solve). Use Common Table Expressions in those databases that support them to traverse. Nested Set (a.k.a Modified Preorder Tree Traversal) First described by Joe Celko - covered in depth in his book Trees and Hierarchies in SQL for Smarties Columns: Left, Right Cheap level, ancestry, descendants Compared to Adjacency List, moves, inserts, deletes more expensive. Requires a specific sort order (e.g. created). So sorting all descendants in a different order requires additional work. Nested Intervals Combination of Nested Sets and Materialized Path where left/right columns are floating point decimals instead of integers and encode the path information. Bridge Table (a.k.a. Closure Table: some good ideas about how to use triggers for maintaining this approach) Columns: ancestor, descendant Stands apart from table it describes. Can include some nodes in more than one hierarchy. Cheap ancestry and descendants (albeit not in what order) For complete knowledge of a hierarchy needs to be combined with another option. Flat Table A modification of the Adjacency List that adds a Level and Rank (e.g. ordering) column to each record. Expensive move and delete Cheap ancestry and descendants Good Use: threaded discussion - forums / blog comments Lineage Column (a.k.a. Materialized Path, Path Enumeration) Column: lineage (e.g. /parent/child/grandchild/etc...) Limit to how deep the hierarchy can be. Descendants cheap (e.g. LEFT(lineage, #) = '/enumerated/path') Ancestry tricky (database specific queries) Database Specific Notes MySQL Use session variables for Adjacency List Oracle Use CONNECT BY to traverse Adjacency Lists PostgreSQL ltree datatype for Materialized Path SQL Server General summary 2008 offers HierarchyId data type appears to help with Lineage Column approach and expand the depth that can be represented.

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  • How to insert hyperlink into access database via sql?

    - by CSharperWithJava
    I have a fairly simple MS Access Database that contains some metadata about a bunch of documents and a hyperlink field that links to the document on our network drive. However, when I use a SQL INSERT statement to populate the hyperlink field, the value I give it only becomes the display text, not the actual link. How can I make the value a functional hyperlink? I'd think that the hyperlink data type would actually create hyperlinks. I'm using Access 2002 SP3.

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  • How do i structure my SQL Database (tables, Schemas, users, stored procedures etc.) to prepare it fo

    - by AlexRednic
    I think the title is self explanatory. What I'm looking for is material so I can further my knowledge. I've never developed a full application before so building one from scratch is a bit overwhelming for me. And the first bump in the road is the database. Websites, articles, books, elaborate answers, anything will do as long as they keep me on the right track. Thanks

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  • How do you hook a C++ compiled dll function to a sql database?

    - by Thomas
    I want to do something like: lastName SIMILARTO(lastName, 'Schwarseneger', 2) where lastName is the field in the database, 'Schwarseneger' is the value that lastName field is being compared to and 2 is the maximum number of characters (edit distance) that can differ between the lastName field, and the entered value. I can implement the SIMILARTO function in C++ using the Levenshtein distance (http://en.wikipedia.org/wiki/Levenshtein_distance), but how do hook the function in a dll to a mySQL implementation?

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  • What database table structure should I use for versions, codebases, deployables?

    - by Zac Thompson
    I'm having doubts about my table structure, and I wonder if there is a better approach. I've got a little database for version control repositories (e.g. SVN), the packages (e.g. Linux RPMs) built therefrom, and the versions (e.g. 1.2.3-4) thereof. A given repository might produce no packages, or several, but if there are more than one for a given repository then a particular version for that repository will indicate a single "tag" of the codebase. A particular version "string" might be used to tag a version of the source code in more than one repository, but there may be no relationship between "1.0" for two different repos. So if packages P and Q both come from repo R, then P 1.0 and Q 1.0 are both built from the 1.0 tag of repo R. But if package X comes from repo Y, then X 1.0 has no relationship to P 1.0. In my (simplified) model, I have the following tables (the x_id columns are auto-incrementing surrogate keys; you can pretend I'm using a different primary key if you wish, it's not really important): repository - repository_id - repository_name (unique) ... version - version_id - version_string (unique for a particular repository) - repository_id ... package - package_id - package_name (unique) - repository_id ... This makes it easy for me to see, for example, what are valid versions of a given package: I can join with the version table using the repository_id. However, suppose I would like to add some information to this database, e.g., to indicate which package versions have been approved for release. I certainly need a new table: package_version - version_id - package_id - package_version_released ... Again, the nature of the keys that I use are not really important to my problem, and you can imagine that the data column is "promotion_level" or something if that helps. My doubts arise when I realize that there's really a very close relationship between the version_id and the package_id in my new table ... they must share the same repository_id. Only a small subset of package/version combinations are valid. So I should have some kind of constraint on those columns, enforcing that ... ... I don't know, it just feels off, somehow. Like I'm including somehow more information than I really need? I don't know how to explain my hesitance here. I can't figure out which (if any) normal form I'm violating, but I also can't find an example of a schema with this sort of structure ... not being a DBA by profession I'm not sure where to look. So I'm asking: am I just being overly sensitive?

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