implement Expr()

engine.go

@@ -558,6 +558,13 @@ func (engine *Engine) Decr(column string, arg ...interface{}) *Session {
 	return session.Decr(column, arg...)
 }
 
+// Method Expr provides a update string like "column = {expression}"
+func (engine *Engine) Expr(column string, expression string) *Session {
+	session := engine.NewSession()
+	session.IsAutoClose = true
+	return session.Expr(column, expression)
+}
+
 // Temporarily change the Get, Find, Update's table
 func (engine *Engine) Table(tableNameOrBean interface{}) *Session {
 	session := engine.NewSession()

session.go

@@ -158,6 +158,12 @@ func (session *Session) Decr(column string, arg ...interface{}) *Session {
 	return session
 }
 
+// Method Expr provides a query string like "column = {expression}"
+func (session *Session) Expr(column string, expression string) *Session {
+	session.Statement.Expr(column, expression)
+	return session
+}
+
 // Method Cols provides some columns to special
 func (session *Session) Cols(columns ...string) *Session {
 	session.Statement.Cols(columns...)
@@ -3237,6 +3243,11 @@ func (session *Session) Update(bean interface{}, condiBean ...interface{}) (int6
 		colNames = append(colNames, session.Engine.Quote(v.colName)+" = "+session.Engine.Quote(v.colName)+" - ?")
 		args = append(args, v.arg)
 	}
+	//for update action to like "column = expression"
+	exprColumns := session.Statement.getExpr()
+	for _, v := range exprColumns {
+		colNames = append(colNames, session.Engine.Quote(v.colName)+" = "+v.expr)
+	}
 
 	var condiColNames []string
 	var condiArgs []interface{}

statement.go

@@ -26,6 +26,11 @@ type decrParam struct {
 	arg     interface{}
 }
 
+type exprParam struct {
+	colName string
+	expr    string
+}
+
 // statement save all the sql info for executing SQL
 type Statement struct {
 	RefTable      *core.Table
@@ -63,6 +68,7 @@ type Statement struct {
 	inColumns     map[string]*inParam
 	incrColumns   map[string]incrParam
 	decrColumns   map[string]decrParam
+	exprColumns   map[string]exprParam
 }
 
 // init
@@ -98,6 +104,7 @@ func (statement *Statement) Init() {
 	statement.inColumns = make(map[string]*inParam)
 	statement.incrColumns = make(map[string]incrParam)
 	statement.decrColumns = make(map[string]decrParam)
+	statement.exprColumns = make(map[string]exprParam)
 }
 
 // add the raw sql statement
@@ -716,6 +723,13 @@ func (statement *Statement) Decr(column string, arg ...interface{}) *Statement {
 	return statement
 }
 
+// Generate  "Update ... Set column = {expression}" statment
+func (statement *Statement) Expr(column string, expression string) *Statement {
+	k := strings.ToLower(column)
+	statement.exprColumns[k] = exprParam{column, expression}
+	return statement
+}
+
 // Generate  "Update ... Set column = column + arg" statment
 func (statement *Statement) getInc() map[string]incrParam {
 	return statement.incrColumns
@@ -726,6 +740,11 @@ func (statement *Statement) getDec() map[string]decrParam {
 	return statement.decrColumns
 }
 
+// Generate  "Update ... Set column = {expression}" statment
+func (statement *Statement) getExpr() map[string]exprParam {
+	return statement.exprColumns
+}
+
 // Generate "Where column IN (?) " statment
 func (statement *Statement) In(column string, args ...interface{}) *Statement {
 	k := strings.ToLower(column)