Add query package with first set of conditions and tests

database/query/condition-and.go

@@ -0,0 +1,31 @@
+package query
+
+// And combines multiple conditions with a logical _AND_ operator.
+func And(conditions ...Condition) Condition {
+	return &andCond{
+		conditions: conditions,
+	}
+}
+
+type andCond struct {
+	conditions []Condition
+}
+
+func (c *andCond) complies(f Fetcher) bool {
+	for _, cond := range c.conditions {
+		if !cond.complies(f) {
+			return false
+		}
+	}
+	return true
+}
+
+func (c *andCond) check() (err error) {
+	for _, cond := range c.conditions {
+		err = cond.check()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}