diff --git a/postgres/numeric/numeric.go b/postgres/numeric/numeric.go
index 8d0cc5e..4988f9e 100644
--- a/postgres/numeric/numeric.go
+++ b/postgres/numeric/numeric.go
@@ -53,6 +53,13 @@ func (n Numeric) IsZero() bool {
 	return float == 0
 }
 
+func (n *Numeric) MatchExpI(exp int32) {
+	diffExp := n.Exp - exp
+	factor := big.NewInt(0).Exp(big.NewInt(10), big.NewInt(int64(diffExp)), nil) //nolint:gomnd
+	n.Exp = exp
+	n.Int = big.NewInt(0).Mul(n.Int, factor)
+}
+
 func (n Numeric) MatchExp(exp int32) Numeric {
 	diffExp := n.Exp - exp
 	factor := big.NewInt(0).Exp(big.NewInt(10), big.NewInt(int64(diffExp)), nil) //nolint:gomnd
@@ -64,6 +71,22 @@ func (n Numeric) MatchExp(exp int32) Numeric {
 	}}
 }
 
+func (n *Numeric) SubI(other Numeric) *Numeric {
+	right := other
+	if n.Exp < other.Exp {
+		right = other.MatchExp(n.Exp)
+	} else if n.Exp > other.Exp {
+		n.MatchExpI(other.Exp)
+	}
+
+	if n.Exp == right.Exp {
+		n.Int = big.NewInt(0).Sub(n.Int, right.Int)
+		return n
+	}
+
+	panic("Cannot subtract with different exponents")
+}
+
 func (n Numeric) Sub(other Numeric) Numeric {
 	left := n
 	right := other
@@ -106,6 +129,22 @@ func (n Numeric) Add(other Numeric) Numeric {
 	panic("Cannot add with different exponents")
 }
 
+func (n *Numeric) AddI(other Numeric) *Numeric {
+	right := other
+	if n.Exp < other.Exp {
+		right = other.MatchExp(n.Exp)
+	} else if n.Exp > other.Exp {
+		n.MatchExpI(other.Exp)
+	}
+
+	if n.Exp == right.Exp {
+		n.Int = big.NewInt(0).Add(n.Int, right.Int)
+		return n
+	}
+
+	panic("Cannot add with different exponents")
+}
+
 func (n Numeric) String() string {
 	if n.Int == nil || n.Int.Int64() == 0 {
 		return "0"