How to get the cartesian product (cross join) of two sets via Excel Formulas

Question

I need to get the cartesian product of two "sets" via Excel 365 Formulas (not VBA, not Power Query). For instance, my two sets are the two left tables, and the expected cartesian product is the right table:

Cartesian product of two sets in Excel 365

How to get the cartesian product with one Excel formula?

If possible, I'd like a general answer, to work for any two sets, whatever values they contain, whatever the number of columns is in the two sets.

The two sets:

Column1	Column2		Column1	Column2
4500005010	A		PO start	D
4500005011	B		header merge	E
4500005012	C		PO activate	F

Answer 1

A generalized option could be:

=CROSSJOIN(Table1,Table2)

Where CROSSJOIN is a custom function defined in Name Manager:

=LAMBDA(array1,array2,
    LET(
        i, SEQUENCE(ROWS(array1)),
        j, SEQUENCE(, ROWS(array2)),
        HSTACK(
            CHOOSEROWS(array1, TOCOL(IF(j, i))),
            CHOOSEROWS(array2, TOCOL(IF(i, j)))
        )
    )
)

Source: https://stackoverflow.com/a/78244826/22459970

If you also wanted the option to handle header rows, CROSSJOIN can be defined as follows:

=LAMBDA(array1,array2,[headers],
    LET(
        incl_h, CHOOSE(headers + 1, 0, 1, 0, 1),
        show_h, CHOOSE(headers + 1, 0, 0, 1, 1),
        a, DROP(array1, incl_h),
        b, DROP(array2, incl_h),
        i, SEQUENCE(ROWS(a)),
        j, SEQUENCE(, ROWS(b)),
        v, HSTACK(
            CHOOSEROWS(a, TOCOL(IF(j, i))),
            CHOOSEROWS(b, TOCOL(IF(i, j)))
        ),
        IF(
            show_h,
            VSTACK(
                IF(
                    incl_h,
                    HSTACK(
                        TAKE(array1, 1),
                        TAKE(array2, 1)
                    ),
                    HSTACK(
                        "tbl1.Col" & SEQUENCE(, COLUMNS(a)),
                        "tbl2.Col" & SEQUENCE(, COLUMNS(b))
                    )
                ),
                v
            ),
            v
        )
    )
)

The optional [headers] argument will behave in a similar fashion to that of the [field_headers] argument of GROUPBY, where the following options are accepted:

• 0 | No
• 1 | Yes but don't show
• 2 | No but generate
• 3 | Yes and show

For example:

=CROSSJOIN(Table1,Table2,2)

Or:

=CROSSJOIN(Table1[#All],Table2[#All],3)

Please note, the line breaks and spaces/indentations were used for improved readability. They can be removed when defining the function in Name Manager.

Answer 2

Cartesian Product

=LET(data1,Table11,data2,Table12,
    Repeat,LAMBDA(fs,ss,by_col,
        TOCOL(IF(TOROW(ss),fs),,by_col)),
    fs,SEQUENCE(ROWS(data1)),
    ss,SEQUENCE(ROWS(data2)),
    HSTACK(CHOOSEROWS(data1,Repeat(fs,ss,0)),
        CHOOSEROWS(data2,Repeat(ss,fs,1))))

TOCOL/IF/SEQUENCE

Efficiency

• Not once have I encountered this combo being more efficient than the INT/MOD combo. Not when using them as they are (no visible difference) but when combined with other functions.
• In this particular case, on two tables of 1000 rows by 5 columns, this combo took 10s while the INT/MOD solution by Mayukh Bhattacharya (the nice one with c, SEQUENCE(a*b),) took 14s. Your MAKEARRAY solution took 23s.

IF/SEQUENCE

• To get more familiar with this combination, feel free to download Repeat Column from my OneDrive.

Answer 3

Without using LAMBDA() helper function:

---

=LET(
     a, TOROW(DataTwo[Column1]&"|"&DataTwo[Column2]),
     b, TOCOL(DataOne[Column1]&"|"&DataOne[Column2]&"|"&a),
     TEXTSPLIT(TEXTAFTER("|"&b,"|",SEQUENCE(,4)),"|"))

---

• Or, Option Two:

=LET(
     a, ROWS(DataTwo),
     b, ROWS(DataOne),
     c, CHOOSEROWS(DataOne,INT((SEQUENCE(a*b)-1)/a)+1),
     d, CHOOSEROWS(DataTwo,MOD((SEQUENCE(a*b)-1),a)+1),
     HSTACK(c,d))

---

Change variables at the end to evaluate:

=LET(
     a, ROWS(DataTwo),
     b, ROWS(DataOne),
     c, SEQUENCE(a*b),
     d, CHOOSEROWS(DataOne,INT((c-1)/a)+1),
     e, CHOOSEROWS(DataTwo,MOD((c-1),a)+1),
     f, HSTACK(d,e),
     f)

---

Answer 4

There's a solution based on MAKEARRAY:

=MAKEARRAY(
  ROWS(Set_1)*ROWS(Set_2),
  COLUMNS(Set_1)+COLUMNS(Set_2),
  LAMBDA(row,col,
         LET(set_num,IF(col<=COLUMNS(Set_1),1,2),CHOOSE(set_num,
            INDEX(Set_1,QUOTIENT(row-1,3)+1,col),
            INDEX(Set_2,MOD(row-1,3)+1,col-COLUMNS(Set_1))))))