示例：筛选序列元素

筛选序列中的元素 - 提取 2013 年 2 月收盘价高于开盘价的日期：

    SELECT symbol, seq_search(day, 20130201, 20130228) as Feb_2013,
        close@Feb_2013 as Feb_Close, open@Feb_2013 as Feb_Open,
        seq_filter(Feb_Close > Feb_Open, Feb_2013) as "up_Feb",
        seq_filter(Feb_Close > Feb_Open, Feb_Open) as "up_Open",
        seq_filter(Feb_Close > Feb_Open, Feb_Close) as "up_Close"
    FROM Quote WHERE symbol='IBM';
     
    symbol
    Feb_2013{}
    Feb_Close{}
    Feb_Open{}
    up_Feb{}
    up_Open{}
    up_Close{}
    ------------------------------------------------------------------------------
    IBM
    {20130201, 20130204, 20130205, 20130206, 20130207, 20130208,
    20130211, 20130212, 20130213, 20130214, 20130215, 20130219,
    20130220, 20130221, 20130222, 20130225, 20130226, 20130227,
    20130228}
    {205.179993, 203.789993, 202.789993, 201.020004, 199.740005, 201.679993,
    200.160004, 200.039993, 200.089996, 199.649994, 200.979996, 200.320007,
    199.309998, 198.330002, 201.089996, 197.509995, 199.139999, 202.330002,
    200.830002}
    {204.649994, 204.190002, 204.309998, 200.389999, 200.619995, 199.970001,
    200.979996, 200.009995, 200.649994, 199.729996, 199.979996, 200.600006,
    200.619995, 198.630005, 199.229996, 201.669998, 198.630005, 198.889999,
    202.179993}
    {20130201, 20130206, 20130208, 20130212, 20130215, 20130222,
    20130226, 20130227}
    {204.649994, 200.389999, 199.970001, 200.009995, 199.979996, 199.229996,
    198.630005, 198.889999}
    {205.179993, 201.020004, 201.679993, 200.039993, 200.979996, 201.089996,
    199.139999, 202.330002}

up_Feb 序列包含了 2013 年 2 月收盘价高于开盘价的日期。为了说明这一点，我们在 up_Feb 序列中突出显示了 2013 年 2 月 8 日的日期值，它与 up_Open 和 up_Close 序列中的第 3 个元素相对应，并且满足筛选条件，即 201.68 > 199.97。

（请注意，多次调用函数 seq_filter() 是必要的，以生成经过筛选的开盘价和收盘价序列，从而使输出更易于理解，因为无法抑制的 Feb_2013、Feb_Open 和 Feb_Close 序列在一定程度上掩盖了关键信息。）

要运行此示例脚本以演示此选择语句，请在 samples/xsql/scripts/financial 目录中使用以下命令：

    x 5