fix: update opengemini/query_expression.go

Co-authored-by: ZhangJian He <[email protected]>

opengemini/query_expression.go

@@ -67,7 +67,7 @@ type AsExpression struct {
 }
 
 func (a *AsExpression) build() string {
-    return fmt.Sprintf("%s as \"%s\"", a.OriginExpr.build(), a.AliasName)
+    return fmt.Sprintf("%s AS \"%s\"", a.OriginExpr.build(), a.AliasName)
 }
 
 func NewAsExpression(aliasName string, expr Expression) *AsExpression {