ORDER BY rand() limit 10000 注:原理:利用rand()函数进行抽取,rand()返回一个0到1之间的 double 值。 Random Sampling 2 优势:faster 缺点:not so random,Hive提供了 sort by,sort by 提供了单个 reducer 内的排序功能,但不保证整体有序,上面的语句是不保证随机性的。 Sample codes: SELECT * FROM tabl...
ORDER BY SortOrder The example above works well if the random value column is required to be present in the rows returned by the query. There is a second approach we can take for returning rows that are sorted by a random value when we don’t need the random value in our result set....
"ORDER BY random()", Song.class) .getResultList(); The JPQL query above will work just fine for PostgreSQL, SQL Server, and MySQL since therandom(),NEWID()orRAND()functions will be passed by Hibernate as-is to the SQL ORDER BY. For Oracle, since the randomness is given by theDBMS_...
repeatseti=i+1;insertintotbl_uservalues((start+i) ,rand_string(8), concat(rand_string(6),'@random.com'),1+FLOOR(RAND()*100),3, now()); until i=max_numendrepeat;commit;end$$-- 将命令结束符修改回来delimiter ;-- 调用存储过程,插入500万数据,需要等待一会时间,等待执行完成callinsert_use...
| oboracle | TPCC | BMSQL_ITEM | NULL | 1 | 0 | zone1 | 172.30.118.75 | 1 | RANDOM | 100000 | 8 | | oboracle | TPCC | BMSQL_CUSTOMER | tpcc_group | 1 | 0 | zone2 | 172.30.118.74 | 1 | RANDOM | 3000000 | 1284 | ...
insert into tbl_user values ((start+i) ,rand_string(8), concat(rand_string(6), '@random.com'), 1+FLOOR(RAND()*100), 3, now()); until i = max_num end repeat; commit; end $$ -- 将命令结束符修改回来 delimiter ; -- 调用存储过程,插入500万数据,需要等待一会时间,等待执行完成 ...
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 ...
rand();random() 返回[0,1)间随机数 round(): 同int() round(x,d):保留基本d位小数 nan():not a number is_nan(x): 判断x是否为nan 注:/与hive有差异!!! presto 10/6=1 hive 10/6=1.6666666666666667 presto 中可采用: cast(10 as double)/6=1.6666666666666667 ...
random() Requires ALTER ANY MASK permission. For function parameters, see Dynamic Data Masking. FILESTREAM Applies to: SQL Server 2008 R2 (10.50.x) and later. Valid only for varbinary(max) columns. Specifies FILESTREAM storage for the varbinary(max) BLOB data. The table must also have a colu...
This strategy is an option when the overall data size is small and you need to address EX page latch contention caused by the following combination of factors:Small row size Shallow B-tree Access pattern with a high rate of random insert, select, update, and delete operations Small tables, ...