An introduction to the
Sometimes when you write a query against a dataset–especially a
query–you just want to see a sample of the data stored in the dataset. One
reason for just returning a sample is that you don’t want to wait the amount of
time it would take to retrieve and render all the data in the dataset into
a table. Some datasets have upwards of a million rows and the time it takes to
SELECT * query against one would be measured in minutes, not seconds.
You might just want to see how the values in the columns are formatted so you
can write a query restricting the rows returned based on the data.
used in a query to return up to a specific number of rows in the results and
comes after the
WHERE clause if there is one.
If we wanted to take a quick pick at some of the data in the Intakes table, we could write this query which limits the rows returned to 10:
SELECT * FROM austin_animal_center_intakes LIMIT 10
And the resultant table would look like:
|A006100||Scamp||2017-12-07T14:07:00||2017-12||Colony Creek And Hunters Trace in Austin (TX)||Stray||Normal||Dog||Neutered Male||10 years||Spinone Italiano Mix||Yellow/White|
|A006100||Scamp||2014-12-19T10:21:00||2014-12||8700 Research Blvd in Austin (TX)||Public Assist||Normal||Dog||Neutered Male||7 years||Spinone Italiano Mix||Yellow/White|
|A191351||Bri-Bri||2015-11-13T15:57:00||2015-11||1912 E William Cannon Rd in Austin (TX)||Stray||Normal||Cat||Intact Female||16 years||Domestic Longhair Mix||Black/White|
|A322813||Tyson||2015-03-05T14:49:00||2015-03||Austin (TX)||Public Assist||Normal||Dog||Neutered Male||11 years||Rottweiler Mix||Black/Brown|
|A553074||Jo Jo||2016-03-27T00:04:00||2016-03||3614 Bill Price in Travis (TX)||Public Assist||Normal||Dog||Spayed Female||7 years||Labrador Retriever/German Shepherd||Brown/Black|
|A672744||Oso||2014-02-17T17:10:00||2014-02||Travis (TX)||Owner Surrender||Normal||Dog||Intact Male||3 years||Rottweiler Mix||Black/Tan|
|A672744||Oso||2014-02-17T17:10:00||2014-02||Austin (TX)||Public Assist||Normal||Dog||Intact Male||3 years||Rottweiler Mix||Black/Tan|
|A672745||*Dottie||2014-02-16T11:01:00||2014-02||Mlk And Fm 969 in Austin (TX)||Stray||Normal||Dog||Spayed Female||2 years||American Staffordshire Terrier Mix||White/Red|
|A672746||Manolo||2014-05-21T13:37:00||2014-05||Austin (TX)||Owner Surrender||Normal||Dog||Neutered Male||9 years||Jack Russell Terrier Mix||White/Black|
|A672746||Manolo||2014-02-16T11:21:00||2014-02||Travis (TX)||Owner Surrender||Normal||Dog||Neutered Male||9 years||Jack Russell Terrier Mix||White/Black|
Note that these results are returned randomly and it is possible that every time you run the query you’ll get a different result set.
Exercises (Continued from previous section)
There are two ways to do these exercises. The first is to use the “Try query” links to test your queries without saving them. The second is to create a data.world project and save your queries to it. If you are reading this documentation and completing the exercises as a tutorial, you will need to create your own project to save your work. Details and instructions are in the SQL tutorial which has instructions for setting up your project and links to all the current exercises.
Using the immunizations table, write a query to show only the first 100 rows of data.
SELECT all the records
immunizations table with the
An introduction to the
WHERE clause and comparison operators.