pj

Plus join

Syntax: x pj y, pj[x;y]

Where

  • x and y are tables
  • y is keyed
  • the key column/s of y are columns of x

returns x and y joined on the key columns of y.

pj adds matching records in y to those in x, by adding common columns, other than the key columns. These common columns must be of appropriate types for addition.

For each record in x:

  • if there is a matching record in y it is added to the x record.
  • if there is no matching record in y, common columns are left unchanged, and new columns are zero.
q)show x:([]a:1 2 3;b:`x`y`z;c:10 20 30)
a b c
------
1 x 10
2 y 20
3 z 30
q)show y:([a:1 3;b:`x`z]c:1 2;d:10 20)
a b| c d
---| ----
1 x| 1 10
3 z| 2 20
q)x pj y
a b c  d
---------
1 x 11 10
2 y 20 0
3 z 32 20

In the example above, pj is equivalent to x+0^y[`a`b#x] (compute the value of y on a and b columns of x, fill the result with zeros and add to x).

Basics: Joins