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 ...
from (select floor(random() * (max(id) - min(id))) as id from test_d) as ma inner join test_d as d on ma.id = d.id; 通过以上方法来做的情况下,每次生产一个随机记录 1.1秒 而 不采用这样的方法直接使用最上面的方法,则需要2.2秒,以上测试时在100万数据行中进行测试的。 最后,来点鸡汤...
The randomness of the result set generated by the previous SELECT statement was due to the NEWID() system function. There's another system function that generates a random value when executed, which is the RAND() system function. If we substitute the NEWID() with the RAND() system function...
ifx_num_rows: 取得返回列的數目。 ifx_free_result: 釋放返回占用內存。 ifx_create_char: 建立字符類。 ifx_free_char: 刪除字符類。 ifx_update_char: 更改字符類。 ifx_get_char: 取得字符類。 ifx_create_blob: 建立長位類。 ifx_copy_blob: 復制長位類。 ifx_free_blob: 刪除長位類。 ifx_get_...
StreamExecutionEnvironment environment = StreamExecutionEnvironment.getExecutionEnvironment(); DataStreamSource<String> source = environment.readTextFile("data/dept.txt"); //所谓的字段重新排序就是查询出来的指定字段顺序可以自定义 StreamTableEnvironment.create(environment).fromDataStream(source,$("f1"))....
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...
DROP PROCEDURE RandomLetterSP 下面的CREATE PROCEDURE示例使用ObjectScript调用Execute(),Fetch()。和Close()方法。此类过程还可以包含FetchRows()和GetInfo()方法调用: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 CREATE PROCEDURE GetTitle() FOR Sample.Employee RESULTS (ID %Integer) CONTAINID 1 LANGUA...
(GETNEXT), 00(OPEN) | 00:SCAN HDFS [db1.table1 t1, RANDOM] partition predicates: CAST(stat_dt AS STRING) >= '2023-05-01', CAST(stat_dt AS STRING) <= '2023-06-01' HDFS partitions=32/1519 files=6400 size=345.03GB stored statistics: table: rows=10.28G size=9.29TB partitions: ...
Declare @d DatetimeSet @d=getdate()SELECT top 1[ActivityID],[CardNo],[Password],[State],[CreateTime],NEWID() as RandomFROM [TGBus_Card].[dbo].[Ka_Card] WhereActivityID=501AndState=0Order By RandomSelect [语句执行花费时间(毫秒)]=Datediff(ms,@d,Getdate()) ...
To optimize performance and reduce random I/O SQL Server might choose to sort all nonclustered index data in memory, and then update all indexes by the order. This is called a wide plan(also called Per-Index Update) and can be forced using this trace flagScope: Global, session, or ...