| tmp1 | CREATE TEMPORARY TABLE `tmp1` ( `id` int(11) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=utf8 | +——-+———-+ 1 row in set (0.00 sec) 内存表 mysql> create table tmp2(id int not null) TYPE=HEAP; Query OK, 0 rows affected (0.00 sec) mysql> show create table tmp2...
Materialize the subquery into an indexed temporary table that is used to perform a join, where the index is used to remove duplicates. The index might also be used later for lookups when joining the temporary table with the outer tables; if not, the table is scanned. For more information a...
Assume that you remove temporary objects such as temporary tables, table variables, or table-valued parameters in SQL Server. In this case, very large PAGELATCH_EX contentions may occur on thesys.sysobjvaluessystem base table. Resolution This fix ...
DROPTABLEIFEXISTSsales_table;CREATETEMPORARYTABLEsales_table(keyvarchar(6),customerIDvarchar(10),productIDvarchar(10),price float);INSERTINTOsales_tableVALUES('1','Customer1','Product1',100),('2','Customer1','Product1',200),('3','Customer1','Product2',100),('4','Customer2','Product2...
EXPLAINSELECT*fromt_table_1wheretask_idin(selectidfromt_table_2whereuid=1) explain后可以看到是走了索引的 到这里可以总结: 1.没有死锁,这点比较肯定,因为没有日志,也符合我们的理解。 2.有慢sql,这点比较奇怪,通过explain select语句是走索引的,但数据库慢日志记录到,全表扫描,不会错。
IF OBJECT_ID('tempdb..#stats_ddl') IS NOT NULL BEGIN DROP TABLE #stats_ddl END For coding consistency, it's a good practice to use this pattern for both tables and temporary tables. It's also a good idea to use DROP TABLE to remove temporary tables when you're finished with them....
create tabletb(idint(4)auto_increment,namevarchar(5),deptvarchar(5),primarykey(id))engine=myISAM auto_increment=1defaultcharset=utf8; SQL优化 1)为什么需要进行SQL优化? 在进行多表连接查询、子查询等操作的时候,由于你写出的SQL语句欠佳,导致的服务器执行时间太长,我们等待结果的时间太长。基于此,我们...
Specify TRUNCATE PARTITION to remove all rows from partition or, if the table is composite partitioned, all rows from partition's subpartitions. Specify TRUNCATE SUBPARTITION to remove all rows from subpartition. If table is index organized, Oracle also truncates any corresponding mapping table ...
• json_remove(字段,'$.键')：删除某个json数据。• ...：还有一些其他json类型的函数，这里不再说明，一般json类型用的较少。• enum(选项1,选项2...选项n)：新增数据时只能从已有的选项中选择一个并插入。• set(选项1,选项2...选项n)：新增数据时可以从已有的选项中选择多个并插入。• eome...
create a matrix table using sql query Create a matrix table using t-sql Create a new database from existing mdf file. Create a percentage from two SUM values Create a query to remove last two characters of a string Create a view and change the data types of some variables Create a writa...