分库的策略是这样的,我们向订单表中插入10条数据,订单表中有订单id和用户id, 订单id我们采用雪花id的生成算法,用户id采用自增的方式,我们又两个库,ds0和ds1, 然后 userId%2, 匹配到不同库中,比如userId是1就保存到ds1库中,userId是2就保存到ds0库中,关于数据库结构,请参看上篇文章,已经给出了sql语句...
This prevents the database from having too many objects, which is a good thing as each additional object in the database costs resources to manage. 2. We can use a single SQL query to accomplish what we want. Notice that we treat the inline view exactly the same as we treat a ...
<outer query: SELECT | INSERT | UPDATE | DELETE | MERGE> 左右滑动查看完整代码 PART 02 为何要在SQL中使用CTE? 通常,在汇总数据或计算复杂公式时,我们需要将查询分成不同的块,以使得代码简洁与易懂。而CTE就能够在此方面帮助到我们。下图展示了我们将上述CTE语句实例化的逐行分析。这段代码被分为了可读性...
This WL adds inlining JSON path expressions in SQL queries to MySQL server. It should allow to execute queries like: SELECT ... FROM t1 WHERE t1.json_field->"$.path.to[0].key"= 123; here 't1.json_field' is the column where specified path is searched, "$.path.to[0].key" is th...
Performance counter stats for '/data/pg16/pghome/bin/psql -p 1101 -h127.0.0.1 -U pg16 postgres -f nj.sql': 3.92 msec task-clock # 0.000 CPUs utilized 13 context-switches # 3.319 K/sec 2 cpu-migrations # 510.542 /sec 282 page-faults # 71.986 K/sec 9,896,281 cycles # 2.526 GHz...
dm_sql_referenced_entities fn_get_sql dm_exec_query_plan fn_builtin_permissions dm_db_index_physical_stats dm_fts_index_keywords_by_document dm_exec_sql_text fn_check_object_signatures dm_cryptographic_provider_algorithms dm_exec_plan_attributes...
-- the query returns a call summary for countries having average call duration > average call duration of all calls SELECT country.country_name_eng, SUM( CASE WHEN call.id IS NOT NULL THEN 1 ELSE 0 END ) AS calls, AVG(ISNULL(DATEDIFF(SECOND, call.start_time, call.end_time),0)) AS...
Note:All the examples of this article will be used on theAdventureworkssample database and queries formatted in theSQL query formatter. Creating an inline table-valued function (iTVF) TheiTVFhas not includedBEGIN/ENDblock in their syntax and theSELECTstatement is the output of this type of fun...
I m currently using the below SQL Server 2019 with compatibility 150Microsoft SQL Server 2019 (RTM-CU18-GDR) (KB5021124) - 15.0.4280.7 (X64) Jan 23 2023...
An inline view is basically a subquery, except it is always in the FROM clause of a SQL statement. The reason it is called a view is because it essentially functions as a view as far as the entire query is concerned. But, remember that an inline view only exists in the query in wh...