网络语T2什么意思-网络语T2什么意思文档介绍内容-阿里云

使用EXPLAIN

本数据库为每个收到查询产生一个查询计划。选择正确的计划来匹配查询结构和数据的属性对于好的性能来说绝对是最...让我们尝试连接两个表，使用我们已经讨论过的列：EXPLAIN SELECT*FROM tenk1 t1,tenk2 t2 WHERE t1.unique1< 10 ANDt1.unique2=...

将文档内容添如 add2Document 结构.add2Document.put("fields",add2DocumentFields);新增对应的文档命令:add add2Document.put("cmd","add");documents.add(add2Document);} System.out.println("push docs："+documents.toString());推送...

语音识别FAQ

语音识别的返回结果JSON中endtime=-1是什么意思？计费类录音文件识别极速版不支持试用吗？功能类实时转写说话有停顿，但是语音识别不断句怎么办？如果是vad断句情况下，实时转写的vad断句依赖对音频中静音数据的判断，如果上游不发送静音...

通过Hint干预执行计划

Seq Scan on t2(cost=0.00.15.50 rows=267 width=8)Filter:(val>1)Optimizer:Postgres query optimizer 以下几种方法可以干预JOIN顺序和JOIN类型：在输出执行计划的语句前添加Hint，语句如下：/*+MergeJoin(t1 t2)Leading((t2 t1))*/...

使用Hint

指定t2与t3先进行HashJoin，随后与t1进行NestLoopJoin：/*+Leading(((t2 t3)t1))HashJoin(t2 t3)NestLoop(t2 t3 t1)*/EXPLAIN SELECT*FROM t1,t2,t3 WHERE t1.val=t2.val and t2.val=t3.val;行号纠正提示以下内容仅适用查询优化器，使用前...

DELETE

DELETE t1,t2 FROM t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.id=t2.id AND t2.id=t3.name LIMIT 10001;DELETE FROM t1,t2 USING t1 INNER JOIN t2 INNER JOIN t3 WHERE t1.id=t2.id AND t2.id=t3.name LIMIT 10001;说明 t1、t2和t3的拆分...

JOIN实现类型

SELECT t1.id,t2.id FROM tj_shop AS t1 JOIN tj_item AS t2 ON t1.id>t2.id 说明数据会膨胀，性能比较差说明链接的表类型为KV/KKV/Summary时，该表的查询条件中必须包含PK等值条件，参考 KV、KKV查询的使用限制。Hash Join：用于包含...

WITH子句

查询和分析语句*|with T1 AS(SELECT host,avg(request_length)length FROM website_log GROUP BY host),T2 AS(SELECT host,avg(request_length)length FROM access_log GROUP BY host)SELECT T1.host,T1.length,T2.length FROM T1 JOIN T2 ...

JOIN操作类型

SELECT t1.id,t2.id FROM tj_shop AS t1 LEFT JOIN tj_item AS t2 ON t1.id=t2.id 说明如果右表值不唯一，建议不要连续使用过多 left join，以免在JOIN过程中产生数据膨胀 Inner Join：内连接。关键字 inner 可以省略。返回满足ON条件的行...

HINT

INSERT/*+Leading(target(t1 t2))*/INTO target SELECT t1.a,t2.b FROM t1 JOIN t2 ON t1.a=t2.a-示例2：SELECT后的Hint只支持指定t1、t2为参数。INSERT INTO target SELECT/*+Leading(t2 t1)*/t1.a,t2.b FROM t1 JOIN t2 ON t1.a=t2.a;...

JOIN操作类型

SELECT t1.id,t2.id FROM tj_shop AS t1 LEFT JOIN tj_item AS t2 ON t1.id=t2.id 说明如果右表值不唯一，建议不要连续使用过多 left join，以免在JOIN过程中产生数据膨胀 Inner Join：内连接。关键字 inner 可以省略。返回满足ON条件的行...

优化聚合与排序

explain select count(*)from t1 join t2 on t1.id=t2.id group by t1.name,t2.name order by t1.name,t2.name;Project(count(*)="count(*)")MemSort(sort="name ASC,name0 ASC")HashAgg(group="name,name0",count(*)="COUNT()")BKAJoin...

Persist plan and Query-Blocker

针对指定SQL Pattern，添加Hints 为相同Pattern的SQL，执行 nested loop join 策略，示例如下：/*+nested_loop_join=true*/PERSIST_PLAN SELECT t1.c1FROM t1 INNER JOIN t2 ON t1.c1=t2.c1 WHERE t1.c2;查询指定SQL是否配置过Hints ...

UPDATE

您可以使用UPDATE语法修改表中符合条件的行。语法单逻辑表 UPDATE[LOW_PRIORITY][IGNORE][schema_name.]tbl_...UPDATE t1,t2 SET t1.name=t2.name WHERE t1.id=t2.name LIMIT 10001;说明 t1和t2的拆分键为ID。相关文献 MySQL UPDATE 语法。

UNION、INTERSECT和EXCEPT

例如，以下查询中，首先计算 T1 和 T2 的 UNION，然后对 UNION 结果执行 EXCEPT 操作。select*from t1 union select*from t2 except select*from t3 order by c1;在同一查询中，组合使用集合运算符时，INTERSECT 运算符优先于 UNION 和 ...

排序优化和执行

如下示例使用了MemSort算子：explain select t1.name from t1 join t2 on t1.id=t2.id order by t1.name,t2.name;返回信息如下：Project(name="name")MemSort(sort="name ASC,name0 ASC")Project(name="name",name0="name0")BKAJoin...

聚合优化和执行

explain select count(*)from t1 join t2 on t1.id=t2.id group by t1.name,t2.name order by t1.name,t2.name;返回信息如下：Project(count(*)="count(*)")MemSort(sort="name ASC,name0 ASC")HashAgg(group="name,name0",count(*)="COUNT...

调整执行计划

prepare s1 as select t.a,t2.avg_b from t join(select avg(b)as avg_b,a from t2 group by a)t2 on t2.a=t.a and t.c<$1 order by t.a;prepare s2 as select t.a,t2.avg_b from t join lateral(select avg(b)as avg_b from t2 where t2.a...

UNION、INTERSECT和EXCEPT

例如，在以下查询中，首先计算T1和T2的UNION，然后对UNION结果执行EXCEPT操作：select*from t1 union select*from t2 except select*from t3 order by c1;在同一个查询中使用运算符组合时，INTERSECT运算符优先于UNION和EXCEPT运算符。例如...

CTE（2.0版）

WITH子句同样适用于多子查询：WITH t1 AS(SELECT a,MAX(b)AS b FROM x GROUP BY a),t2 AS(SELECT a,AVG(d)AS d FROM y GROUP BY a)SELECT t1.*,t2.*FROM t1 JOIN t2 ON t1.a=t2.a;WITH子句中定义的关系可以互相连接：WITH x AS(SELECT a ...

表设计最佳实践

Update（将table2表中的记录的值更新到table1表中）INSERT OVERWRITE TABLE table1 SELECT t1.key1,t1.key2,CASE WHEN t2.key1 IS NOT NULL THEN t2.col1 ELSE t1.col1 END AS col1,CASE WHEN t2.key2 IS NOT NULL THEN t2.col2 ELSE t1....

ODPS-0130252

FAILED:ODPS-0130252:[3,1]Cartesian product is not allowed-cartesian product is not allowed without mapjoin-正确，补充join条件，这里join条件是两个表的字段相等 odps>select t1.*from src t1 join src t2 on t1.key=t2.key;...

Hash Join的并行加速

workers:4)(cost=10.82 rows=4)->Parallel inner hash join(t2.c2=t1.c1)(cost=0.57 rows=1)->Parallel table scan on t2,with parallel partitions:1(cost=0.03 rows=1)->Parallel hash->Parallel table scan on t1,with parallel ...

CDN加速静态资源时如何设置服务器端的缓存过期时间

当对象的 Last-Modified 为 20140801 00:00:00，当前时间Curtime为 20140802 00:00:00，则t1=(Curtime-Last_modified)*0.1=8640s，t2=max(10,t1)=8640s，t=min(t2,3600)=3600s，那么缓存时间为3600s。当对象的 Last-Modified 为 20140801 ...

并行查询Hint语法

在t1表上做并行扫表，然后将数据做shuffle分发到下一阶段Workers-在t2表上做并行扫表，然后将数据做shuffle分发到下一阶段Workers-在下阶段Workers上完成co-location join后，结果汇总到Leader SELECT/*+PARALLEL(t1)PARALLEL(t2)PQ_...

ePQ支持分区表查询

segments:6)->Append->Hash Join Hash Cond:(t2_p1.id=t3_p1.id)->Partial Seq Scan on t2_p1->Hash->Full Seq Scan on t3_p1->Hash Join Hash Cond:(t2_p2.id=t3_p2.id)->Partial Seq Scan on t2_p2->Hash->Full Seq Scan on t3_p2->Hash ...

ePQ支持分区表查询

segments:6)->Append->Hash Join Hash Cond:(t2_p1.id=t3_p1.id)->Partial Seq Scan on t2_p1->Hash->Full Seq Scan on t3_p1->Hash Join Hash Cond:(t2_p2.id=t3_p2.id)->Partial Seq Scan on t2_p2->Hash->Full Seq Scan on t3_p2->Hash ...

Common Table Expression简介

CTE ON t2.i1=T_CTE.i1_cte AND t2.i2=T_CTE.i2_cte 也可以在JOIN中去使用它：WITH T_CTE(i1_cte,i2_cte)AS(SELECT i1,i2 FROM t1)SELECT*FROM t2 WHERE EXISTS(SELECT*FROM T_CTE WHERE t2.i1=i1_cte AND t2.i2=i2_cte)或者在子查询中去...

Common Table Expresssion（>=3.7.5）简介

CTE ON t2.i1=T_CTE.i1_cte AND t2.i2=T_CTE.i2_cte 你也可以在JOIN中去使用他，WITH T_CTE(i1_cte,i2_cte)AS(SELECT i1,i2 FROM t1)SELECT*FROM t2 WHERE EXISTS(SELECT*FROM T_CTE WHERE t2.i1=i1_cte AND t2.i2=i2_cte)或者在子查询中去...

Common Table Expresssion（>=3.7.5）简介

CTE ON t2.i1=T_CTE.i1_cte AND t2.i2=T_CTE.i2_cte 你也可以在JOIN中去使用他，WITH T_CTE(i1_cte,i2_cte)AS(SELECT i1,i2 FROM t1)SELECT*FROM t2 WHERE EXISTS(SELECT*FROM T_CTE WHERE t2.i1=i1_cte AND t2.i2=i2_cte)或者在子查询中去...

获取创建列存索引的DDL语句

执行结果如下：mysql>call dbms_imci.columnar_advise_by_columns('select count(t1.a)from t1 inner join t2 on t1.a=t2.a group by t1.b');DDL_STATEMENT|+-+|ALTER TABLE test.t1 MODIFY COLUMN a int(11)DEFAULT NULL COMMENT '...

ST_nearestApproachDistance

float8 ST_nearestApproachDistance(trajectory traj,timestamp t1,timestamp t2,geometry g);参数参数名称描述 traj 轨迹对象。t1 开始时间。t2 结束时间。range 时间段。g 几何对象。示例 Select ST_nearestApproachDistance(traj,'...

增量查询

Transactional Table 2.0支持增量写入和存储，最重要的一个考虑就是支持增量查询以及增量计算优化，为此，专门设计开发了新的...如果begin是t1，end是t2-1，即查询的时间范围为（t1,t2），这个时间段是没有任何增量数据插入的，会返回空行。

ST_nearestApproachDistance

float8 ST_nearestApproachDistance(trajectory traj,trajectory traj2,timestamp t1,timestamp t2);参数参数名称描述 traj1 轨迹对象1。traj2 轨迹对象2。t1 开始时间。t2 结束时间。range 时间段。示例 Select ST_...

ST_nearestApproachDistance

float8 ST_nearestApproachDistance(trajectory traj,trajectory traj2,timestamp t1,timestamp t2);参数参数名称描述 traj1 轨迹对象1。traj2 轨迹对象2。t1 开始时间。t2 结束时间。range 时间段。示例 Select ST_...

ST_nearestApproachDistance

float8 ST_nearestApproachDistance(trajectory traj,trajectory traj2,timestamp t1,timestamp t2);参数参数名称描述 traj1 轨迹对象1。traj2 轨迹对象2。t1 开始时间。t2 结束时间。range 时间段。示例 Select ST_...

关联子查询上拉

EXPLAIN(COSTS OFF,ANALYZE)SELECT*FROM t1 WHERE t1.a IN(SELECT a FROM t2 WHERE t2.b=t1.b AND t2.b=1);QUERY PLAN-Seq Scan on t1(actual time=67.631.1641827.119 rows=100000 loops=1)Filter:(SubPlan 1)SubPlan 1->Result(actual ...

关联子查询上拉

EXPLAIN(COSTS OFF,ANALYZE)SELECT*FROM t1 WHERE t1.a IN(SELECT a FROM t2 WHERE t2.b=t1.b AND t2.b=1);QUERY PLAN-Seq Scan on t1(actual time=67.631.1641827.119 rows=100000 loops=1)Filter:(SubPlan 1)SubPlan 1->Result(actual ...

原理架构

存储创建完成并检查存储处理于正常同步中之后，T2 时刻创建全量 DumpWriter，并开始同步 T2 时刻的全量数据；在 T3 时刻完成了全量同步，这时 T2 到 T3 时间段的增量数据是在存储中；T4 时间创建增量 Writer，并从 T1 时刻开始拉取增量数据...

ST_intersection

geometry ST_intersection(trajectory traj1,trajectory traj2,timestamp t1,timestamp t2);参数参数名称描述 traj1 轨迹对象1。traj2 轨迹对象2。t1 开始时间。t2 结束时间。range 时间段。示例 Select ST_intersection((Select traj ...

网络语T2什么意思

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