I want to select about 5,000 of those rows at random.我想随机选择大约5,000行。I've thought of a complicated way, creating a temp table with a "random number" column, copying my table into that, looping through the temp table and updating each row withRAND(), and then selecting from ...
1. Select a random row with Microsoft SQL Server: SELECT TOP 1 column FROM tableORDER BYNEWID() 1. Select a random row with IBM DB2 SELECT column, RAND() as IDX FROM table ORDER BY IDX FETCH FIRST 1 ROWS ONLY 1. ThanksTim Select a random record with Oracle: SELECT column FROM( SEL...
SELECT TOP 1 column FROM table ORDER BY NEWID() Select a random row with IBM DB2: SELECT column, RAND() as IDX FROM table ORDER BY IDX FETCH FIRST 1 ROWS ONLY Select a random record with Oracle: SELECT column FROM ( SELECT column FROM table ORDER BY bms_random.value ) WHERE rownum ...
SELECT * FROM table ORDER BY RANDOM() LIMIT 1; 35投票 以下解决方案比anktastic的快得多(count(*)花费很大,但如果你可以缓存它,那么差异应该不会那么大),它本身比“order by random()快得多” “当你有大量行时,尽管它们有一些不方便。 如果你的 rowids 相当拥挤(即很少删除),那么你可以执行以下操作...
with get_date_interval as ( -- 获取总体的开始、结束日期:这里只是一个电表 -- 多个电表注意后续的逻辑该带分组的分组 select min(period_start) as all_start , max(period_end) as all_end from data_exercise.dwd_electricity_usage_records ) , get_inner_months as ( -- 获取两个日期之间有多少个...
create(settings); // 创建输入表 String sourceSql = "CREATE TABLE datagen_table (\n" + " word STRING,\n" + " frequency int\n" + ") WITH (\n" + " 'connector' = 'datagen',\n" + " 'rows-per-second' = '1',\n" + " 'fields.word.kind' = 'random',\n" + " 'fields....
VALUES(default,'普货40吨需13米半挂一辆','上海市','上海市','2015-10-05 08:13:59',ROUND((random()*10000)::NUMERIC,2)); row_number() 返回行号,不分组 postgres=# select row_number() over(),* from bills limit 2; row_number | id | goodsdesc | beginunit | begincity | pubtime ...
可将一个或两个时间段列标记为 HIDDEN 标志,以隐式隐藏这些列,这样 SELECT * FROM <table> 就不会返回这些列中的值。 默认情况下,时间段列不处于隐藏状态。 若要使用隐藏的列,则它必须显式包含在直接引用时态表的所有查询中。 若要更改现有时间段列的 HIDDEN 特性,须先删除 PERIOD,再使用不同的隐藏标志重新...
DECLARE sqlset_cur DBMS_SQLTUNE.SQLSET_CURSOR; BEGIN DBMS_SQLTUNE.CREATE_SQLSET('SUB_STS1', 'test purpose'); OPEN sqlset_cur FOR SELECT value(p) FROM table( DBMS_SQLTUNE.SELECT_SQLPA_TASK( task_name => 'SPA_TASK1', execution_name => 'COMP', level_filter => 'REGRESSED')) p;...
Block Sampling 优势:fast 缺点:not random Sample codes: SELECT * FROM table_sample TABLESAMPLE(10 ROWS) Sampling Bucketed Table 优势:fast and random Sample codes: SELECT * FRO…阅读全文 赞同2 添加评论 分享收藏 Hive多维分析函数—With cube、Grouping sets、With rollup 1.应用...