Multiple Joins

def qapi = api.queryApi()

def t1 = qapi.tables().products()
def t2 = qapi.tables().companyParameterRows("ProductGroup")
def t3 = qapi.tables().companyParameterRows("ProductLine")
def t4 = qapi.tables().companyParameterRows("SubCategory")

return qapi.source(t1, [t1.sku(), t1.ProductGroup, t1.ProductLine, t1.SubCategory])
        .leftOuterJoin(t2, { cols -> [t2.ProductGroupName] },
                { cols ->
                    qapi.exprs().and(
                            t2.ProductGroup.equal(cols.ProductGroup)
                    )
                }
        )
        .leftOuterJoin(t3, { cols -> [t3.ProductLineName] },
                { cols ->
                    qapi.exprs().and(
                            t3.ProductLine.equal(cols.ProductLine)
                    )
                }
        )
        .leftOuterJoin(t4, { cols -> [t4.SubCategoryName] },
                { cols ->
                    qapi.exprs().and(
                            t4.SubCategory.equal(cols.SubCategory)
                    )
                }
        )
        .stream { it.collect { it } }