func (c *QueryConditionSet) Or() *QueryConditionSet {
	c.qs = append(c.qs, "OR")
	return c
}
Or adds OR to the set.
package sqlutil
import (
	"fmt"
	"reflect"
	"strings"
)
type QueryConditionSet struct {
	qs []string
	qv []interface{}
}
func Cond() *QueryConditionSet {
	return &QueryConditionSet{}
}
func (c *QueryConditionSet) Equal(k string, v interface{}) *QueryConditionSet {
	c.qs = append(c.qs, fmt.Sprintf("%s=?", k))
	c.qv = append(c.qv, v)
	return c
}
func (c *QueryConditionSet) In(k string, v interface{}) *QueryConditionSet {
	n := 0
	walkSlice(v, func(fv reflect.Value) {
		n++
		c.qv = append(c.qv, fv.Interface())
	})
	c.qs = append(c.qs, fmt.Sprintf("%s IN %s", k, genbindgroup(n)))
	return c
}
func (c *QueryConditionSet) InSelect(k string, v *SelectStmt) *QueryConditionSet {
	c.qs = append(c.qs, fmt.Sprintf("%s IN (%s)", k, v.String()))
	c.qv = append(c.qv, v.values...)
	return c
}
func (c *QueryConditionSet) And() *QueryConditionSet {
	c.qs = append(c.qs, "AND")
	return c
}