SQL, or “Structured Query Language”, is a means of asking questions of, and updating data in, relational databases. Here area some examples
- "Which version of Greenplum Database software, am I running on the cluster?"
Alternatively, the psql command utility can be used for the same, as following:
psql -d <database-name> -c "SELECT version();"
In both cases, the query result would be similar to
version |
PostgreSQL 8.3.23 (Greenplum Database 5.7.0 build commit:f7c6eb5cc61b25a7ff9c5a657d6f903befbae013) on x86_64-pc-linux-gnu, compiled by GCC gcc (GCC) 6.2.0, 64-bit compiled on Mar 30 2018 14:19:06 |
(1 row) |
- "Which version of PostGIS extension, am I running on the Greenplum Database cluster?"
SELECT postgis_full_version();
version |
POSTGIS="2.1.5 r13152" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel. 4.8.0, 6 March 2012" GDAL="GDAL 1.11.1, released 2014/09/24" LIBXML="2.7.6" LIBJSON="UNKNOWN" RASTER |
(1 row) |
- “What is the population of the City of New York?”
SELECT
SUM(popn_total) AS population
FROM
nyc_census_blocks;
population |
8,175,032.00 |
(1 row) |
- “What is the population of the Bronx?”
SELECT
SUM(popn_total) AS population
FROM
nyc_census_blocks
WHERE
boroname = 'The Bronx';
population |
1,385,108.00 |
(1 row) |
- “For each borough, what percentage of the population is white?”
SELECT
boroname,
100 * Sum(popn_white)/Sum(popn_total) AS white_pct
FROM
nyc_census_blocks
GROUP BY
boroname;
boroname
| white_pct
|
Queens |
39.72207739459101 |
Brooklyn |
42.80117379326865 |
Manhattan |
57.44930394804628 |
Staten Island |
72.8942034860154 |
The Bronx |
27.903744689944755 |
5 rows |
Geometry (PostGIS) SQL exercises