Feat: select without from and with recursive

[Angelelz]

This will close #372 and will close #209. Also related to #1215?

This PR depends on #1218.

Upon merging, It will be possible to write a select statement without the .from() method. That will make possible to create recursive statements like the following (adapted from mysql docs example):

const fibonacci = db.$withRecursive('fibonacci').as((qb) =>
  qb
    .select({
      n: sql<number>`1`.as('n'),
      fibN: sql<number>`0`.as('fibN'),
      nextFibN: sql<number>`1`.as('nextFibN'),
      goldenRatio: sql<string>`cast(0 as decimal(5,4))`.as('gRatio'),
    })
    .unionAll((_, fibonacci) =>
      qb
        .select({
          n: sql<number>`${fibonacci.n} + 1`,
          fibN: fibonacci.nextFibN,
          nextFibN: sql<number>`${fibonacci.fibN} + ${fibonacci.nextFibN}`,
          goldenRatio: sql<
            string
          >`case when ${fibonacci.fibN} = 0 then 0 else ${fibonacci.nextFibN} / ${fibonacci.fibN} end`,
        })
        .from(fibonacci.as("recFib"))
        .where(and(lt(fibonacci.n, 10)))
    )
);

const result = await db.withRecursive(fibonacci).select().from(fibonacci);

And the result will be:

[
  { n: 1, fibN: 0, nextFibN: 1, goldenRatio: '0.0000' },
  { n: 2, fibN: 1, nextFibN: 1, goldenRatio: '0.0000' },
  { n: 3, fibN: 1, nextFibN: 2, goldenRatio: '1.0000' },
  { n: 4, fibN: 2, nextFibN: 3, goldenRatio: '2.0000' },
  { n: 5, fibN: 3, nextFibN: 5, goldenRatio: '1.5000' },
  { n: 6, fibN: 5, nextFibN: 8, goldenRatio: '1.6667' },
  { n: 7, fibN: 8, nextFibN: 13, goldenRatio: '1.6000' },
  { n: 8, fibN: 13, nextFibN: 21, goldenRatio: '1.6250' },
  { n: 9, fibN: 21, nextFibN: 34, goldenRatio: '1.6154' },
  { n: 10, fibN: 34, nextFibN: 55, goldenRatio: '1.6190' },
]

Please take a look at this tweet for another example.

[mylescarrick]

This is so brilliant – I'm using this in my app, working with recursive data structures in postgres. Is there anything I can do to help move it toward review?

[lxia1220]

I used kysely to write hierarchy structure sql, this pr works well for me in most cases.
Is there any blocker for it?

[adamgreg]

This would be really helpful for me. Any chance it will make it into the next release?

[scape76]

any updates? +1 to the above @dankochetov

[mpost]

I would be very happy to see this PR being merged. Working with postgres generate_series would be much more viable.

[johaven]

+1

[JohnAllenTech]

Again +1 to this. Very much a blocker for me at the minute not to have this functionality.

[goto3]

+1

[mikkelwf]

+1

[jonataslaw]

Firstly, thank you for your work.
Second: I really need this.
Third, the PR that you indicated as pending has already been merged into master, is there any reason for it not to be merged now?