如何将值添加到列字段中的现有值，然后将更新值插入另一个表

Question

I Have a members table with a column amount which already has an integer value in it, I wish to add to that value and then use its contents to update another table called accounts which holds the amount being credited and the new balance (ie After addition)

   $this->query_array = array(':amt' =>  $amount, ':uid' => $userid, ':dat' => $date );

    $this->query_string = "UPDATE members SET amount = amount + :amt;
                           INSERT INTO accounts VALUES ( :uid, :amt, members.amount + :amt,  :dat);";

Thats my query above, am trying to get the members.amount table from the update query and use it in the insert query is there a better way, one that works than what I tried.

Sample Data :

         Members Table      userid       amount
                             ---------------------
                               u123        4000
                               y123        5000

          Accounts Table      userid       credit   balance    date

Accounts table is currently empty so what I wanna do is add 300 to all values in memebrs table and then insert into accounts something like this.

          Accounts Table      userid       credit   balance    date
                              -------------------------------------
                                u123       300      4300       11-11-11
                                y123       300      5300       11-11-11

Answer 1

It's a simple insert by a select query, the only question is about the date

INSERT INTO Accounts (userid, credit, balance, date)
  SELECT userid, 300, amount, NOW()
    FROM Members;

Answer 2

I would use an insert ... select ... statement to achieve the desired outputs:

INSERT INTO accounts
SELECT members.userid, :amt, members.amount,  :dat FROM members

Notes:

1. I'm using the members.amount in place of members.amount + :amt because the :amt has already been added once to members.amount .

2. Your update statement updates all records within the members table, yet the insert statement would create records for a specific user only. I believe you should restrict the update statement to the specific user only or not restrict the insert to a specific user. I chose the latter approach.

3. If you want to store the balance in a denormalised way, then I would rather use a trigger on the accounts table to update the balance in the members table, than to use 2 statements.