Acronym for Structured Query Language. A syntax for retrieving and manipulating data from a relational database.

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31
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11answers
18k views

How to connect to PostGIS database from ArcMap?

How can I connect to a PostGIS database from ArcMap? Solutions for ArcGIS 9.3, 10.0 and later are acceptable. Ideally, I would like to be able to perform spatially enabled queries and receive the ...
45
votes
2answers
7k views

Acquiring ArcGIS-like speed in Postgis

I have been using Postgis 2.0 for 3/4 of a year now and while I really enjoy using it, excessive query processing time has rendered it basically unusable for my use case. I tend to do heavy ...
11
votes
1answer
2k views

How to use ST_DelaunayTriangles to construct a Voronoi diagram?

With PostGIS 2.1+ we can use ST_DelaunayTriangles() to generate a Delaunay triangulation, that is a dual graph of its Voronoi diagram, and, in theory, they have an exact and reversible conversion. ...
9
votes
3answers
14k views

Converting MultiLinestring to Linestring with PostGIS?

I have a multiline string and want to convert it to a linestring in order to use some functions that only work with linestrings. I used ST_Dump() and got a collection of my geometries. If I merge them ...
7
votes
3answers
6k views

Select features by attribute if in Python list

I believe this will amount to largely a sql syntax question. Essentially, I am trying to complete a select by attribute in Python but based on the query of whether an attribute is present in a list. ...
8
votes
1answer
4k views

SELECT TOP query in ArcGIS Desktop?

Is there a way to use a SELECT TOP (n) within ArcGIS desktop? Is appears that since the ArcGIS query builder is effectively building the SQL statement after the WHERE clause, that this may not be ...
3
votes
2answers
1k views

ArcObjects: Alternative workflow to using a SQL query with over 1000 values in IN statement

I have a ListBox listing the unique values of a column in a feature class; the user can select any number of values and click a button to then zoom to the set of features matching those values. A ...
27
votes
4answers
14k views

What is the best way to join lots of small polygons to form a larger polygon?

I have the following layer using SRID 27700 in postgis: It's every administrative region in the UK, and (as you can see from the colour grouping) each of them has a text field specifying the county ...
18
votes
5answers
7k views

A SQL console in QGIS

I know QGIS comes with its field calculator, which is not bad. It also comes with ftools which permits several operations on geometry and attributes. But we often need more control and I haven't seen ...
6
votes
1answer
4k views

STIntersects - Update field to give me count of points in polygon

I have a points layer (dbo.ptLayer) Around 1M points Spatial Geometry Type (dbo.ptLayer.geom) No spatial index just yet, but will create one once data gathering complete. I have a polygon layer ...
11
votes
3answers
2k views

How to interpolate GPS Positions in PostGIS

I have a PostGIS table of GPS positions for every five seconds: 2011-01-01 00:00:05, POINT(x1,y1) 2011-01-01 00:00:10, POINT(x2,y2) 2011-01-01 00:00:15, POINT(x3,y3) ... I'm looking for a query ...
6
votes
2answers
7k views

ARCGIS 10 definition query to select the max value from a group

In ARCGIS 10 I am trying to do a Definition Query that will select the records that are the max values from a specific group. Here is what I have tried in the Query Builder but I am getting an "the ...
5
votes
1answer
1k views

ogr2ogr selecting features by attributes

I am writing a shapefile after some processing; however, in the final step I need to do some selection by attributes from the the shapefile. I am using the command in a shell with the aim of using it ...
1
vote
2answers
3k views

How to select all points within a circle in PostGIS?

I have set of points in a PostGIS Table (Type Geometry). Now, I need to filter points that lie in a circle with a center (C) and radius (R)! I expect C to be of type Point or Coordinates.. R to be ...
8
votes
3answers
3k views

Label points at regular intervals using ArcGIS for Desktop?

I'm working with lines on roads represented by a large number of sequencial points. Since labeling all of them would make the points impossible to identify, I'd like to know if there is a way to label ...
4
votes
1answer
1k views

Cartodb - SQL query of public visualization of a private table

The team at CartoDB have recently(last few days) made some useful updates that now allow public visualisation maps to reference data in private tables. The change has only been made in the last day ...
2
votes
2answers
2k views

Merge lines with the same 'name' attribute on QGIS?

I have a shapefile with a few thousand lines, each is a street segment. I'd like to merge all features with the same 'streetName' attribute into a single attribute. I only really care about the name ...
2
votes
1answer
778 views

Select top 5 most items in a geodatabase

I'd like to know what is the best way to select the 5 most expensive items (in terms of actual monetary value) in my geodatabase where i have a price field. Prices are not necessarily ordered but can ...
8
votes
3answers
6k views

How to find nearest neighbors between two tables with point locations in SpatiaLite?

I have started playing with SpatiaLite today and already stumbled upon a problem. For each point location stored in tableOne I would like to select one, nearest (linear distance) point from tableTwo. ...
3
votes
3answers
2k views

How to Calculate length of polyline geometry for several tables in PostGIS?

PostGIS database contains several geometry (polyline) tables (with names "D1_r", "D2_r", "D3_r"). I calculate length for one "postgis layer" use request: SELECT ...
2
votes
1answer
507 views

How to split polygons with another polygon and inheritage data?

Let's say that we have two tables with polygons representing areas. Table A and Table B. Geometries from table A represents both the valid and invalid areas. And the geometries in table B represents ...
7
votes
1answer
862 views

Join based on maximum overlap in PostGIS/PostGresQL?

I have two sets of polygons in two tables. The sets overlap each other. For each polygon in set A, I would like to get the ID of the polygon in set B that it overlaps the most. I'm using PostgreSQL ...
2
votes
1answer
425 views

Raster as Attribute Field Error

I'm using Arc 10.1. I am creating a parcel inventory where I would like to have a photo of the property attached as an attribute and view-able with an HTML popup. I have a polygon feature class built ...
4
votes
2answers
1k views

SQL Syntax to extract (convert) Strings with Degrees Minutes to Decimal Degrees

I have a PostgreSQL/PostGIS database with a two string fields containing Lat and Long coordinates in degrees and decimal minutes, like this 45° 24.5' N 3° 43.01' E. How can I convert them into ...
4
votes
1answer
626 views

How to populate SQL options for parameter in ArcGIS 10 tool?

I'm trying to create a tool where individuals can select a variety of records using a SQL expression that is then passed to a calculation. I can add a parameter under the tool, and select SQL ...
2
votes
1answer
284 views

Get list of all tables in CartoDB account with SQL statement?

How can I get a list of all available tables in my own authenticated CartoDB account with a SQL statement? This returns null: SELECT table_name as t FROM information_schema.tables WHERE table_schema ...
1
vote
1answer
359 views

nearest neighbor query in SpatiaLite

I am trying to find the nearest line to each point in a layer, and I have over 1 million points. I want to be able to associated the closest unique line ID with the point unique IDs. I have tried to ...
1
vote
2answers
79 views

SQL query new feature with loop

I'm trying to create an individual buffer feature class for each column of an input feature class, where there is a field that contains the buffer distance. I think there is a problem with my SQL ...
1
vote
1answer
306 views

Why does this SQL syntax produce empty feature class with ArcGIS Select_analysis?

I'm working on a script that involves an arcpy.select_analysis function. The problem I have is that when I run the script it produces an empty file. I've verified that the whole thing works when in ...
1
vote
1answer
961 views

Labeling classes for small roads on large extent maps in ArcMap with SQL statement?

I have many small sub divisions that won't label nice, (lot of overlapping) unreadable. While using the bullet leader symbol. What would be the best statement that would place the labels in a ...
0
votes
1answer
2k views

How can I show numbers as percentages in CartoDB?

I would like to format numbers as percentages in cartodb. What are the best functions to display numbers with decimals, comma separators or percenteges? Thanks
13
votes
1answer
2k views

Identifying topological relationships using PostGIS

I'm trying to perform a basic typology analysis using PostGIS. My objective is to find any polygons that touch other polygons. To do this, I thought the ST_GetFaceEdges would work (reference). I want ...
11
votes
1answer
669 views

Nearest Neighbor Grouped Selection in QGIS

OK - so I have an interesting problem I am trying to solve. I have a list containing over 100,000 points in lat/long format which I have imported into qgis. Now, what I am trying to do here is group ...
8
votes
4answers
4k views

ST_Intersection slow query

I am trying to perform an intersection between two layers: Polyline layer representing some roads (~5500 rows) Polygon layer representing irregularly shaped buffers around various points of interest ...
8
votes
4answers
2k views

Queries returning very big datasets in PostGIS

I have a PostGIS query that will return several million rows: SELECT t1.id AS id1, t2.id AS id2, ABS(t1.mean_h - t2.mean_h) AS h_diff, ST_Distance(t1.the_geom, t2.the_geom) AS dist FROM ...
7
votes
3answers
2k views

Join intersecting lines with PostGIS

This is something that I'm almost ashamed to ask but I can't seem to get it to work for the life of me. I have a road layer with segments, each segment has a Road ID and a segment type. I would like ...
7
votes
1answer
844 views

PostGIS Intersection and Summarise Attributes

I am usually an ArcGIS desktop user, but keen to start using PostGIS more and I have a really big bit of processing to do. Not sure what functions to use, hopefully someone can help. I have a polygon ...
11
votes
2answers
10k views

Creating spatial tables with PostGIS

In the PostGIS documentation it says that there are two steps to creating a spatial table with SQL: Create a normal non-spatial table. Add a spatial column to the table using the OpenGIS ...
9
votes
3answers
4k views

Beginner PostGIS question: getting geometry from multiple tables

I am very new to PostGIS, PostgreSQL, and SQL in general. I have 44 tables in my PostGIS database, and each one represents a different layer of vector data. Each was loaded from a separate shapefile, ...
8
votes
1answer
2k views

How to trace SQL queries sent by ArcGIS Server (ArcSDE) to Oracle database?

I'd like to generate a log file containing all SQL queries sent by ArcGIS Server (ArcSDE) to Oracle database. Is there a way to do so? I'm using Oracle 11g and ArcGIS Server 10.0 on Windows. ArcSDE is ...
7
votes
2answers
3k views

SQL query to have a complete geojson feature from PostGIS

I would like to get a geojson feature with properties from PostGIS. I have found an example to have a feature collection but I can't make it works for just a feature. so far I tryed to modify the ...
7
votes
1answer
2k views

Performance Gain Through GIST Index for Point in Polygon Query

I have two tables: locations(id,region_id,the_geom) and regions(id,the_geom). For each location point I want to determine the region it is located in: UPDATE locations SET region_id = (SELECT id ...
6
votes
2answers
2k views

GDAL SQL syntax to add field an put values

I try to make a new field in my attribute table and put in values from another field after converting from character to integer but can't get the right syntax. I run this as shell-script in MSYS. cd ...
4
votes
2answers
930 views

Plotting large numbers of objects on a chart using R and WKT format

I am retrieving thousands of geometry lines in WKT format from a Microsoft SQL Server database. I would like to plot all of those lines in one map, but I am having some difficulty with the code. How ...
3
votes
3answers
2k views

Trigger on SQL Server 2008 ArcSDE 10 and ArcGIS Server 10

I need to build a sql server db trigger to update a date field with the current date when a record is inserted or updated, I think. I will be using the date field as a way to recognize ...
0
votes
1answer
2k views

query syntax to select every multiple of nn record (shapefile) [duplicate]

I have data like multiples of 40. 40 80 120 160 200 and so on. I would like to label every record that is a multiple of 100. I have tried a couple of methods and cant get them to work either as a ...
11
votes
3answers
4k views

Intersecting a raster with a polygon using PostGIS - artefact error

I'm using PostGIS2.0 to do some raster/polygon intersections. I'm having difficulty understanding which operation I should use, and what the quickest way of performing this is. My problem is as ...
8
votes
2answers
4k views

Import large CSV file into PostGIS

I am trying to import CSV files into PostGIS. Following this post, I have created tables before. I found other suggestions saying that I can run the copy command. If I run this command: COPY table ...
8
votes
3answers
6k views

Bounding box for PostGIS table

Is there an easy way to get the bounding box for an entire table in PostGIS? Thanks
6
votes
3answers
831 views

How to Comment Out Definition Queries

I use Definition Queries a lot in my daily GIS life, but one of the many things I've found annoying about ArcMap is the inability to comment out Definition Queries. I'd like to have this option as ...