1.2 主从原理架构 MySQL主从同步至少需要用到2台服务器,一台为master库,另一台为slave库,要实现复制首先需要在master上开启bin-log日志功能,bin-log日志用于记录在Master库中执行的增、删、修改、更新操作的sql语句,整个过程需要开启3个线程,分别是Master开启IO线程,Slave开启IO线程和SQL线程。 2. 准备实验环境 这个...
# 指定某一列的内容作为 metric name 的后缀 field_to_append = "" # 语句执行超时时间 timeout = "3s" # 查询语句,连续三个单引号,和Python的三个单引号语义类似,里边内容就不用转义 request = ''' select 'n9e' as service, count(*) as total from n9e_v5.users ''' 自定义SQL的配置,想...
order by countz desc; This query returns the three stratum/treatment combinations that have rows for them, but does not return the one combination that has no rows. I've tried using an NVL on the count but to no avail—it just seems to stop processing once it determines that there ar...
--实例:SELECT count( distinct 编号) as 计数 FROM T进度总表 sum --计算整数列的合 --实例:select sum(数量小计) as 合计 from T数据源 getdate() --获得服务器当前日期时间函数 --实例:select count(distinct 出库单号) as 计数 from T进度总表 WHERE datediff(day,出库时间,getdate())=0...
Here is my sql so far... SELECT t1.customerID, SUM(Case WHEN notr = "10" THEN t1.value Else 0 End) invoiceValue, SUM(Case WHEN notr = "16" THEN t1.value Else 0 End) creditValue FROM table t1 GROUP BY customerID I need to get the InvCount (2) and CreditCount (1) into ...
SQL_ASYNC_MODE SQL_ASYNC_NOTIFICATION SQL_BATCH_ROW_COUNT SQL_BATCH_SUPPORT SQL_DATA_SOURCE_NAME SQL_DRIVER_AWARE_POOLING_SUPPORTED SQL_DRIVER_HDBC SQL_DRIVER_HDESC SQL_DRIVER_HENV SQL_DRIVER_HLIB SQL_DRIVER_HSTMT SQL_DRIVER_NAME SQL_DRIVER_ODBC_VER SQL_DRIVER_VER SQL_DYNAMIC_CURSOR_ATTRIBU...
GET DIAGNOSTICS@c1=NUMBER,@c2=ROW_COUNT; 要获取条件信息,需要指定条件编号并将所需条件项检索到目标变量中。如下示例中,GET DIAGNOSTICS实例将SQLSTATE值和错误消息分配给了用户变量@c3和@c4: GET DIAGNOSTICS CONDITION3@c3=RETURNED_SQLSTATE,@c4=MESSAGE_TEXT; ...
GET DIAGNOSTICS@c1=NUMBER,@c2=ROW_COUNT; 要获取条件信息,需要指定条件编号并将所需条件项检索到目标变量中。如下示例中,GET DIAGNOSTICS实例将SQLSTATE值和错误消息分配给了用户变量@c3和@c4: GET DIAGNOSTICS CONDITION3@c3=RETURNED_SQLSTATE,@c4=MESSAGE_TEXT; ...
SQL_BATCH_ROW_COUNT SQL_BATCH_SUPPORT SQL_DATA_SOURCE_NAME SQL_DRIVER_AWARE_POOLING_SUPPORTED SQL_DRIVER_HDBC SQL_DRIVER_HDESC SQL_DRIVER_HENV SQL_DRIVER_HLIB SQL_DRIVER_HSTMT SQL_DRIVER_NAME SQL_DRIVER_ODBC_VER SQL_DRIVER_VER SQL_DYNAMIC_CURSOR_ATTRIBUTES1 SQL_DYNAMIC_CURSOR_ATTRIBUTES2 SQ...
SQL 是声明式语言,即对用户来说,只关心它能做什么,不用关心它怎么做。这样可能会产生潜在的性能问题:排序,会产生排序的代表性运算有下面这些 GROUP BY 子句 ORDER BY 子句 聚合函数(SUM、COUNT、AVG、MAX、MIN) DISTINCT 集合运算符(UNION、INTERSECT、EXCEPT) ...