SELECT * FROM (SELECT x.PARENT_CLIENT ,sum(x.PS_L_AMOUNT)/100000000 as total FROM glsc_data.ti_trpt_temp_bill_his x WHERE x.beg_date::date =to_date('2023-05-24','yyyy-MM-dd') GROUP BY x.PARENT_CLIENT) s order by s.total desc limit 3 ，把这段代码做行转列操作用postgresql，但不要用tablefunc扩展

可以使用CASE语句实现行转列操作，以下是一个示例代码：

SELECT 
    s.client AS client,
    SUM(CASE WHEN s.rnk = 1 THEN s.total ELSE 0 END) AS total_1,
    SUM(CASE WHEN s.rnk = 2 THEN s.total ELSE 0 END) AS total_2,
    SUM(CASE WHEN s.rnk = 3 THEN s.total ELSE 0 END) AS total_3
FROM (
    SELECT 
        x.PARENT_CLIENT AS client,
        SUM(x.PS_L_AMOUNT) / 100000000 AS total,
        ROW_NUMBER() OVER (PARTITION BY x.beg_date::date ORDER BY SUM(x.PS_L_AMOUNT) DESC) AS rnk
    FROM glsc_data.ti_trpt_temp_bill_his x
    WHERE x.beg_date::date = to_date('2023-05-24','yyyy-MM-dd')
    GROUP BY x.PARENT_CLIENT
) s
GROUP BY s.client
ORDER BY s.client;

这段代码首先使用了子查询计算每个客户在指定日期的总金额，并按照金额进行降序排列并分配排名。然后在外部查询中使用CASE语句将每个客户的前三名金额转换为列。最后按照客户名称排序输出。