在SQL语法里面,有unique和distinct两个关键字, unique是distinct的同义词,功能完全相同。 distinct是标准语法,其他数据库 sql server,db2,oracle,sybase,mysql等都支持。 unique,oracle、informix数据库认识,其他数据库有的认识,有的不认识。 以后方便数据库移植,推荐使用distinct。 大家要注意此项,当遇到1486 error: 0...
distinct这个关键字来过滤掉多余的重复记录只保留一条,但往往只用 它来返回不重复记录的条数,而不是用它来返回不重记录的所有值。其原因是distinct只有用二重循环查询来解决,而这样对于一个数据量非常大的站来说,无疑是会直接影响到效率的。 下面先来看看例子: table表 字段1 字段2 id name 1 a 2 b 3 c ...
DISTINCT_KEYS Decimal 不同的索引值数。对于强制使用 UNIQUE 和 PRIMARY KEY 约束的索引,此值与表中的行数相同 (USER_TABLES.NUM_ROWS)。 AVG_LEAF_BLOCKS_PER_KEY Decimal 平均叶块数,索引中的每个不同值舍入到最接近的整数。对于强制使用 UNIQUE 和 PRIMARY KEY 约束的索引,此值始终为 1。
The Entity ID is the set of unique attributes that identifies the entity. Data Augmentation Spreadsheet Use this spreadsheet that contains Entities and Entity ID mapping details for CX. Select "Entity" in the Data augmentation flow. 6-1 7 Subject Areas Subject Areas This chapter provides ...
In making the transition, you must address unique challenges, answer foundational questions, and seize far-reaching opportunities. The road to cloud is not clearly paved. No single approach, architecture, or set of services will be useful for all cloud applications. ...
INTEGRATION_ID string 80 A unique identifier for the record. TENANT_ID string 80 - X_CUSTOM string 10 - Table 5-5 shows the structure of the file_acct_budget.csv file. The records in the file_acct_budget.csv will be loaded into W__ACCT_BUDGET_F. Table 5-5 Universal Source for ...
Managing your field workers requires unique processes, tools, and considerations. But the investment in field service management software can provide some substantial benefits. Coordinate and monitor employee schedules, customer appointments, and timelines. Save time and gas with appointment optimization ...
We are studying the punctual structures, i.e., the primitive recursive structures on the whole set of integers. The punctual categoricity relative to a com
A connection pool is created for each unique connection string. When a pool is created, multiple connection objects are created and added to the pool so that the minimum pool size requirement is satisfied. Connections are added to the pool as needed, up to the maximum pool size. ...
create or replace view vstu as select * from student; 重新编译视图 alter view v_ss compile; ~物化视图 -- 更改会话级别的日期显示 alter session set nls_date_format='YYYY-MM-DD HH:MI:SS'; select distinct dname from dept; select dname from dept group by dname; ...