join_multi.go

// heavily borrowed from Rosetta Code example
package main

import (
	"fmt"
)

type row map[string]interface{}

var (
	tableA = []row{
		row{"name": "Jonah", "female": 0, "age": 27},
		row{"name": "Alan", "female": 0, "age": 18},
		row{"name": "Glory", "female": 0, "age": 28},
		row{"name": "Popeye", "female": 0, "age": 18},
		row{"name": "Alan", "female": 1, "age": 28},
	}

	tableB = []row{
		row{"name": "Jonah", "female": 0, "fear": "Whales"},
		row{"name": "Jonah", "female": 0, "fear": "Spiders"},
		row{"name": "Alan", "female": 0, "fear": "Ghosts"},
		row{"name": "Alan", "female": 1, "fear": "Zombies"},
		row{"name": "Glory", "female": 0, "fear": "Buffy"},
	}
)

func main() {
	Join(tableA, tableB, "name", "female")
	//	t := Join(tableA, tableB, "name", "female")
	//	j, _ := json.MarshalIndent(t, "", "\t")
	//	fmt.Println(string(j))
}

func Join(t1, t2 []row, on ...string) []map[string]interface{} {
	m := []map[string]interface{}{}

	for a := 0; a < len(t1); a++ {

		for b := 0; b < len(t2); b++ {

			var matches int

			for i := range on {

				if t1[a][on[i]] == t2[b][on[i]] {
					matches += 1
				}

			}

			if len(on) == matches {

				fmt.Println(t1[a], t2[b])

				r := row{}
				for k, v := range t1[a] {
					r[k] = v
				}
				for k, v := range t2[b] {
					r[k] = v
				}
				m = append(m, r)
			}
		}
	}
	return m
}