A command used to retrieve information from a database

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28
votes
3answers
2k views

Is there a “Select by Attributes” plugin/widget for ArcGIS Server JS API?

I'm hoping to find some existing code which emulates the "Select by Attributes" dialog in ArcMap, within the ArcGIS Server JavaScript API. Writing a hard-coded QueryTask is easy - I'm looking for ...
19
votes
2answers
6k views

How to select features with NULL attributes in QGIS?

I need to identify which features have null attributes in the attribute table of a shapefile. When i try [field]= 'NULL' it selects the features with value=0 (see picture) Suggestions?
15
votes
1answer
479 views

How to query OSM for all beaches facing west? - QGIS preferred

I want to identify all beaches on this planet (or a given subset of it) that are facing westwards (+/- 20-30 degrees). My idea is to use OSM as the data source. Extracting all polygons that have the ...
14
votes
3answers
11k views

Idiots guide to expressions for QGIS

I have no formal training in GIS and have learned on the fly with ArcGIS 9.3 at work and have been dabbling with QGIS on my own time for my business. Is there any resource recommendations ingeneral ...
12
votes
6answers
5k views

How to identify duplicate attributes in a field?

I have a point shapefile with thousand of points. It has an ID code field that supposed to be unique. Every now and then the data entry clerk wrongly type the id creating duplicates.Right now I'm ...
11
votes
2answers
4k views

How can I more efficiently select related records?

Below is the code I'm using to replicate the "related tables" button in ArcMap. In ArcMap that button selects features in one feature class or table based on the selection of features in another ...
11
votes
3answers
1k views

Are personal geodatabases better suited for quickly querying indexed attributes than file geodatabases?

I'm preparing data for an ArcGIS Engine application that queries the data to search for an address. Sometimes we search just on the street name field, just on the house number field, or both. When ...
10
votes
3answers
2k views

How to speed up queries for raster databases?

I have a raster database in postgresql/postgis with these columns: (ID, rast, data_of_data). 'rast' is the column that has raster files in WKT format. An example query to find the DN value of a ...
10
votes
2answers
1k views

What is the precision of SELECT DISTINCT on PostGIS geometry column?

I wonder what the precision of the SELECT DISTINCT operator is on a PostGIS geometry. On my system, the following query gives me a count of 5, which means that the inserted points are considered equal ...
9
votes
3answers
5k views

How to query all records (>1000) and export to csv?

I posted in arcgis forum but never got any answer. Can anyone tell me how to solve this? Assume you have a vehicle tracking records from Oct.1 to Dec. 31 with wind speed information. All data is ...
9
votes
2answers
366 views

Is it possible to use comments in QGIS Query Builder with shapefiles?

I am trying different queries in the Query Builder. Is there a way to comment the query? I tried with /* */ # -- without success : An error occurred when executing the query. The data ...
9
votes
1answer
964 views

ST_ClosestPoint(line, point) does not intersect line

In my PostGIS database (PostGIS 1.5 on Postgres 8.4.1), I have two tables: roads (composed of linestrings) and crashes (composed of points). I've been trying to correlate each crash to a road, but I'm ...
8
votes
3answers
1k views

How to select only Spatial tables from the postgres database?

My database contains both Spatial and Non-Spatial tables, but I want to retrieve only Spatial table from the query. Any suggestions to select only Spatial tables. 'the_geom' is the geometry column in ...
8
votes
2answers
277 views

Find headwater polygons

This is a follow up question to this question. I have a river network (multiline) and some drainage polygons (see picture below). My goal is to select only the headwater polygons (green). With ...
7
votes
2answers
2k views

How do I use QGIS python console to iterate through simple layer queries and png outputs?

I'm really new to QGIS coding and I'm having a hard time finding (especially) the api classes/functions to carry out actions of the Query Builder window. I'm basically trying to do this: Iterate ...
7
votes
3answers
256 views

What would be 'normal' processing time for a large postgis query

I have two datasets which I want to spatially join (with an intersect). The first dataset consists of 9 million addresses. The second dataset consists of 12.000 neighbourhoods. I want the add the ...
7
votes
2answers
434 views

How to run a spatial query with a raster and vector layer in QGIS?

I have a soil map (vector-polygon layer) and a map of the crops farmed in the same area (raster layer, from the US Cropland Data Layer). I would like to calculate for a given soil type, the surface ...
6
votes
1answer
773 views

Need to learn more about Precision and Accuracy

I am currently taking Introduction to Image Interpretation online and there is a section in it that talks about Precision and Accuracy. I wanted to know if someone out there has any good information ...
6
votes
1answer
3k views

How do I perform a proximity search with Postgis?

OK, so I downloaded the Geonames database (cities1000) and wrote a small Ruby program to import them into my table (geo_cities). I then added geography column called geog. So after all of that, I ...
6
votes
1answer
3k views

How can i search over my layers with openlayers?

i have my map running over geoserver and openlayers. but i want to add a search box to find places in it. Well not specifically places but directions. The map reads the layers directly over geoserver ...
6
votes
1answer
3k views

How to find the nearest point by using PostGIS function?

table A: lat | long | the_geom | code | sign 13.8433095 | 100.6360357 | 0101000020E61.... | ABC | start_point 13.7544738 | 100.5459646 | 0101000020E6..... | ABC | end_point 13.4124215 | 100.6232332 ...
6
votes
2answers
534 views

Find start of river

Edit: Follow-up question here (= Find headwater polygons). How can I determine the start of a river in PostGIS? I have a river network (Multiline) and want to find the startpoints of the rivers. ...
6
votes
1answer
784 views

How to sum area of polygons by values occuring in multiple fields?

My data has 2 fields holding landuse types, which both describe what is within the polygon. For example, the polygon may have Type1=Retail, Type2=Leisure Area= 1 but another polygon has Type1=Leisure, ...
6
votes
0answers
148 views

Postgis database query optimisation

I have a set of rasters in DTED format which I load into postgis database using raster2pgsql command line tool. Each of rasters is simply stored in a row and described by rid and a value of raster ...
5
votes
1answer
173 views

How to build a query/expression to select specific points within a buffer? (in QGIS)

I have a point layer in QGIS. Each point represents a tree and each tree has information about its height as an attribute. I would like to build a query/expression to select all those trees that have ...
5
votes
2answers
771 views

How can I extract all distinct values from a PostGIS Raster?

I am working with an integer raster in PostGIS 2.1 and I would like to extract all distinct values in that raster. I was hoping to be able to do something along the lines of the following query, but I ...
5
votes
1answer
2k views

How to Find points in a Kilometre radius

I am new to PostGIS and GeoData. I need to find where the lightning has stroke by a period of time and kilometre radius based on a given location. I have given lon/lat and my table is: latitude ...
5
votes
3answers
6k views

How to fix performance problem in PostGIS ST_Intersects?

I'm a newbie in postgis and I have a problem in query performance. This my query: SELECT DISTINCT ON (userid) userid ,ST_AsText(position), timestamp FROM table1 WHERE ST_Intersects ( ...
5
votes
2answers
1k views

Selecting maximum Value based on other field using ArcMap?

I have problems with a SQL query. The table looks like this, it is a point feature class both in postgres and file geodatabase, I am working in ArcMap. name: elev_p HEIGHT AREAid 100 1 200 1 ...
5
votes
2answers
2k views

PostgreSql query problem with aggregate functions

I need help with a PostgreSql query. I need to find all parcels which have bigger area then average. I'm using this query: SELECT OBJECTID FROM parcela WHERE ST_Area(geom)<(SELECT ...
5
votes
2answers
463 views

Query a georss feed

I'm trying to consume a georss feed from a C# project. Can I have queries against a #georss feed? For example 'nearest item to Lon/Lat' or 'items contained in bounding box X' .? Thanks
5
votes
1answer
3k views

Querying Data with a 1-Many Relationship Class

I have created a relationship class similar to the one I posted about in this question. Essentially, there is a point feature class representing a location of vegetation clearing with attributes ...
5
votes
2answers
638 views

QGIS Filtering Multiple Values using Query Builder

I am a complete beginner in QGIS, so I'm sorry if I don't use the right terminology. In the "Query Builder" I can currently filter on value from the "Values List", but I'd like to be able to filter ...
5
votes
2answers
988 views

How to run custom queries on vector layers and display results?

Is there a way to display the result of a query in QGIS? For instance : To get the total number of inhabitants : SELECT SUM( inhabitants ) FROM countries To get the total density : SELECT ...
5
votes
1answer
322 views

How to build query expression to display text from one-to-many relationship in ArcMap?

I have two tables in an enterprise geodatabase stored in PostgreSQL and accessed via ArcSDE: parcel and person 1 or + parcel can have 1 or + person (relationship is pll_person) I can display all ...
5
votes
4answers
115 views

uDig window to change between historical dates?

I'm new to uDig, but I'm experienced Java developer. I have points with temperature measurements that change overtime in SQL database. I would like to give user ability to change between historical ...
5
votes
3answers
2k views

How can I export or query all hospitals from Open Street Map?

I'd like to extract all the hospital locations in the US from Open Street Map as a reference for my geocoding project. I know how to get all the OSM data for a small area with the QGIS plugin but not ...
5
votes
2answers
2k views

How to speed up an st_intersects() query?

I have a "huge" spatial database: 72GB, 200 millions documents with geometries (points) I have a GIST index on the geometries the database: CREATE TABLE resources ( id bigint NOT NULL, accuracy ...
5
votes
2answers
1k views

Practical way of managing polygons and unions of them

I have a table in PostGIS with a quite fine partition of a region, which I'd like to dissolve at two higher levels by means of two foreign keys (e.g. municipality and state). The partition is a real ...
5
votes
1answer
181 views

ESRI Javascript FeatureLayer Select by Attributes

I am trying to select a group of features in an ESRI javascript API featureLayer by attribute. The call errors out. My code is as follows. Here is the layer definition: var fieldDefs = [{ ...
4
votes
3answers
916 views

How to create Where Clause from user input via Python list?

I am trying to perform a query based on values in a Python list. The where clause will then be used in an Update Cursor, so that the rows NOT equal to the values in the list will be deleted. This is ...
4
votes
2answers
1k views

What is the best approach to using IQueryFilter.WhereClause in ArcObjects?

What is your preferred / best approach to using IQueryFilter.WhereClause statements in ArcObjects (e.g. when selecting features by attributes)? You need to check the source type (shapefile / personal ...
4
votes
2answers
2k views

Postgis, get the points that are x meters near another point, in meters

I'm trying to find the points within a certain distance, in meters, from another point. I'm using the function ST_Buffer, but I don't get how to express the distance in meters. I'm trying with ...
4
votes
2answers
1k views

Spatial query of raster data

I have population distribution data as a raster layer and exposure contours as vector (polygon) layers. What I'd like to do is use the vector layer to estimate the population indicated from the raster ...
4
votes
3answers
3k views

Selecting MAX values within records with the same name

I'm working in ArcMap 9.3 and I've never dealt with that kind of queries... I need to Select the MAX value from column [A] for each set of records in the table which have the same value in column [B] ...
4
votes
2answers
193 views

How to query for a specific point, within a specific polygon?

I have a shapefile points layer, with each point representing either Marginal, suboptimal, or optimal conditions. I want to find only the marginal points within a specific polygon from my catchments ...
4
votes
1answer
442 views

Improve database performance for geospatial

I have a database with osm data imported with osmosis tool. I want to search for the nearest POIs from a given point. For this purpose, I perform this query: select id from nodes where ...
4
votes
1answer
7k views

How to filter features in a layer?

I am trying to display certain features in a shapefile-based layer using QGIS. I have found the subset function in the properties panel, which does exactly what i want, but is too tedious given that I ...
4
votes
1answer
766 views

Reading OGC geometry data from SQL server using R

I would like to write a script in R that creates a map using OGC geometry data that is stored on a Microsoft SQL server. Is there a way to read OGC geometry data using a query passed from R? Maybe ...
4
votes
3answers
3k views

How to join two tables using date, time, lat and lon as common field?

I am sorry if the question is elementary but I did not find any clear discussion or guide to understand how to run a query in postgresql. So that a pointer to another website would be also useful. ...