How to use UNION/UNION_ALL?

[darylhjd]

Following this issue #69, I am trying to add a variable number of expressions into UNION.

	var firstArg SelectStatement
	tuples := make([]SelectStatement, 0, len(rows)-1)
	for idx, row := range rows {
		statement := SELECT(
			String(row.UserID),
			... // more columns
		)

		if idx == 0 {
			firstArg = statement
		} else {
			tuples = append(tuples, statement)
		}
	}

	inputRows := CTE(
		"input_rows",
	).AS(
		UNION(firstArg, firstArg, tuples...),
	)

Since the function requires at least 2 arguments, I am duplicating the first row, and then the rest of the input is programmatically created.

Problem with this approach is that the type of the slice is wrong, and jet.SerializableStatement doesn't seem to be an exportable type by the package, so I am stuck. What is the correct way to do this?

Maybe a more general question: Given a slice of structs, I would like to convert it into a table that I can use. How do I do it?

[houten11]

Maybe something like this:

	// first two rows       
	stmt := UNION(
		SELECT(String(row[0].UserID).AS("first")/*, more columns*/),
		SELECT(String(row[1].UserID)/*, more columns*/),
	)

	// the rest of rows 
	for i := 2; i < len(rows); i++ {
		stmt = UNION(
			stmt,
			SELECT(String(row[i].UserID)/*, more columns*/),
		)
	}