Q´ tal , solo qiero decir q funcionó de esta manera:
Código:
select min(inicio) from (
SELECT MIN(FechaIniCon) AS inicio
FROM t1
WHERE (Cedula = @cedula) AND (FechaIniCon IS NOT NULL)
UNION
(SELECT MIN(FechaIniAcu) AS Expr1
FROM t2
WHERE (Cedula = @cedula) AND (FechaIniAcu IS NOT NULL)
UNION
SELECT MIN(FechaInicio) AS Expr1
FROM t3
WHERE (Cedula = @cedula) AND (FechaInicio IS NOT NULL))) as t1