Código SQL [-] select 'Factura' as tipo, nro_factura AS numero from facturas union select 'Remision' as tipo, nro_remision AS numero from remisiones union select 'Compras' as tipo, nro_compra AS numero from compras
select 'Factura' as tipo, nro_factura AS numero from facturas union select 'Remision' as tipo, nro_remision AS numero from remisiones union select 'Compras' as tipo, nro_compra AS numero from compras