More Interview Questions Flashcards
What is .Q.dpft?
Save table function in the Q namespace.
What is Q.hdpf?
Save tables function in the Q namespace.
What does exec mean?
returns selected rows and columns from a table.
What is each right?
applies a list of paramaters on the right to a single parameter on the left
What is each left?
applies a list of paramaters on the left to a single parameter on the right
What is each right?
applies a list of parameters on the right to a single parameter on the left
What are splayed tables why do we use them?
When a table is too large to fit into memory, we can break it into pieces and save each column individually under a directory with the table name.
What are segmented tables why do we use them?
Extension of partitioned databases. The root directory has a sym file and a par.txt file. Data partitions are stored in separate locations.
How can you modify on disk data.
using amend ~
What is .z.w
handle dictionary.
What is .z.p?
loca/UTC timespan.
.Q.par?
locate partition
What is par.txt?
defines the top-level partitioning of the database into directories. Each row of par.txt is a directory path. Each such directory is itself partitioned in the usual way, typically by date.
0h?
mixed list
How to delete from namespace?
delete from `.ns
What is a window join?
type of as of join.
select syntax.
select <return> by <grouping> from <table> where <filter></filter></grouping></return>
select 4 columns from a table
select date, sym, open, size from daily
How do you select columns and rename them in one line.
select dt: date, stock:sym, open, sz: size from daily
How to create a column from a function on an ald column?
select avg: 0.5*high+low from table
How to find the sum of a column from a list
select sum column from table
How would you find the wavg price of google stock
SELECT vwap:size wavg price
FROM trade
WHERE sym=`GOOG
How to find indexes of all Apple stocks
where table[sym] = AAPL
how to find the max size of each sym
select max size by sym from table
