Does `sqlite3` support loops? - sqlite

Question

I wrote the little bash script below and it works as intended, but I added couple comments and newlines for readability which breaks the code. Removing comments and newlines should make it a valid script.
### read all measurements from the database and list each value only once
sqlite3 -init /tmp/timeout /tmp/testje.sqlite \
'select distinct measurement from errors order by measurement;' |
### remove the first line of stdout as this is a notification rather than intended output
sed '1d' |
### loop though all found values
while read error; do
### count the number of occurences in the original table and print that
sqlite3 -init /tmp/timeout /tmp/testje.sqlite \
"select $error,count( measurement ) from errors where measurement = '$error' ;"
done
The result is like this:
134 1
136 1
139 2
159 1
Question: Is it possible with sqlite3 to translate the while-loop to SQL statements? In other words, does sqlite3 support some sort of for-loop to loop through results of a previous query?
Now I know sqlite3 is a very limited database and chances are that what I want is just too complex for it. I've been searching, for it but I'm really a database nitwit and the hits I get so far are either on a different database or solving an entirely different problem.
The easiest answer (that I do not hope for BTW) is 'sqlite3 does not support loops'.

Answer 1

SQLite does not support loops. Here is the entire language, you'll notice that structured programming is completely absent.
However, that's not to say that you can't get what you want without loops, using sets or some other SQL construct instead. In your case it might be as simple as:
select measurement, count( measurement ) from errors GROUP BY measurement
That will give you a list of all measurements in the errors table and a count of how often each one occurs.
In general, SQL engines are best utilized by expressing your query in a single (sometimes complex) SQL statement, which is submitted to the engine for optimization. In your example you've already codified some decisions about the strategy used to get the data from the database -- it's a tenet of SQL that the engine is better able to make those decisions than the programmer.