!427 update docs/uniCloud/cf-database-dbcmd.md.

Merge pull request !427 from NightWhite/N/A

docs/uniCloud/cf-database-dbcmd.md

@@ -98,8 +98,8 @@ function and(...expressions: Expression[]): Command
 
  
 ```js
-let res = await const dbCmd = db.command
-db.collection('todo').where({
+const dbCmd = db.command
+let res = await db.collection('todo').where({
   progress: dbCmd.gt(80).or(dbCmd.lt(20))
 }).get()
 ```