The table alias must be used in place of the actual table name if the table name appears in the WHERE clause before a column name. Additionally, one needs to use the alias while specifying the table in the SELEC
如果有t表的status字段,只有两个值0和1, 0对应的记录数比较少, 1对应大部分记录,在status字段上创建了索引,那么 select * from t where status=0 走索引是高效的, 而select * from t where status=1 走索引就是低效的,还不如全表扫描. 补充:如果是古老的RBO,只要有索引就会使用不管是否高效;而CBO是有选...
1.对于分区表,必须指定分区,否则会报错No parttion predicate found for Alias xxx Table xxx. 2.使用了order by,则必须使用limit。提示信息为In strict mode,if ORDER BY is specified ,LIMIT must also be specifiied. 3.禁止笛卡尔积查询。提示信息为:In strict mode, cartesian product is not allowed. 使...
Explanation:where name_of_table_or_column is the column of the table name to which we have to assign the alternative name and name_of_alias is the alternative or temporary name with which the table of the column to which it is assigned can be referred further in the query statement. We ...
-- 员工名称翻译,如果同一个缓存则可以同时对几个字段进行翻译 --> <translate cache="staffIdName" columns="staffName,createName" /> <filters> <!-- 反向利用缓存通过名称匹配出id用于精确查询 --> <cache-arg cache-name="staffIdNameCache" param="staffName" alias-name="staffIds"/> </filters>...
经过分析发现,原来 sls-cn-guangzhou-queries 中的 query 数据并不包含latencyMs这个字段,它的数据中对应的字段名称实际上为latency。针对这种情况,我们仍然可以通过 SPL 的extend 算子解决这种问题,即为 latency 字段增加一个 alias 字段(当前 SPL 会默认将所有字段作为 varchar 处理,下面 SPL 中进行了类型转换)。
使用别名(alias),别名用AS关键字赋予 SELECT TRIM(CONCAT(vend_name ,'(', vend_country,')')) AS vend_title FROM Vendors ORDER BY vend_name; SELECT vend_name AS VENDNAME FROM Vendors; 3.执行算术运算: SELECT prod_id, quantity, item_price, quantity*item_price AS expanded_price FROM OrderIte...
I had initially written this query in TOAD editor and it worked perfectly. In trying to convert it to Outsystems syntax, I added the AS in front of the alias. I got that from another post, similar to this subject. Upon your suggestion, I copied the code from the Executed SQL tab...
需要去掉重复的alias,order by子句再进行引用。 in.subquery.without.result colx in subquery没有返回任何结果,则colx在源表中不存在的问题。 错误写法: select * from table_name where not_exist_col in (select id from table_name limit 0); 报错信息: FAILED: ODPS-0130071:[2,7] Semantic analysis exc...
可以通过定义以下别名来修改调用isql以使用 sqlcmd 的现有脚本: alias isql="sqlcmd -D"sqlcmd 最佳做法使用以下方法来帮助实现最高的安全性和效率。使用集成安全性。 在自动化环境中使用 -X[1]。 使用适当的文件系统权限保护输入文件和输出文件。 若要提高性能,请在一个 sqlcmd 会话中执行尽可能多的操作,而...