obclient> CREATE TABLE tbl1(col1 INT PRIMARY KEY, col2 INT); Query OK, 0 rows affected obclient> INSERT INTO tbl1 VALUES(1,1),(2,2),(3,3),(4,4); Query OK, 4 rows affected Records: 4 Duplicates: 0 Warnings: 0 obclient> SELECT * FROM tbl1; +---+---+ | COL1 | COL...
而truncate的操作在MySQL是一个很快的操作,数据转瞬即逝,在Oracle中有一些差别,可能这些数据还有恢复的可能。 比如我们在Oracle端创建一个表空间,创建两个表test_del,test_tru; 创建表空间 create tablespace test_data datafile '/U01/app/oracle/oradata/newtest2/test_data.dbf' size 10M autoextend on; 创建...
If there are many duplicates, this can take a long time. Luckily Oracle Database has many tricks to help youdelete rows faster. How to Prevent More Duplicates You've gone to all the effort of removing the duplicates. You're feeling good. But a week later a new ticket comes in: "Pleas...
#执行InnoDB的碎片回收mysql>altertableuserengine=InnoDB;QueryOK,0rowsaffected(9.00sec)Records:0Dupli...
SQL> delete from test_del; 68314 rows deleted. select *from test_tru; 而truncate操作在Oracle,MySQL都是一个极快的过程,在Oracle中不会直接抹去数据,数据还是依旧存在,在一定的条件下触发才会回收。 我们使用dbms_rowid来解析一下 SQL> select dbms_rowid.ROWID_RELATIVE_FNO(rowid) as file#,dbms_rowid....
SQL> delete from test_del; 68314 rows deleted. select *from test_tru; 而truncate操作在Oracle,MySQL都是一个极快的过程,在Oracle中不会直接抹去数据,数据还是依旧存在,在一定的条件下触发才会回收。 我们使用dbms_rowid来解析一下 SQL> select dbms_rowid.ROWID_RELATIVE_FNO(rowid) as file#,dbms_rowid....
In the case of an extract, the source system might be able to fix the extract or remove duplicates before you ingest the file. This is more efficient in multiple ways. It uses fewer network resources and also simplifies your ETL process. And generally, the data owner will understand the da...
1SELECT句法23SELECT[STRAIGHT_JOIN]4[SQL_SMALL_RESULT][SQL_BIG_RESULT][SQL_BUFFER_RESULT]5[SQL_CACHE | SQL_NO_CACHE][SQL_CALC_FOUND_ROWS][HIGH_PRIORITY]6[DISTINCT | DISTINCTROW | ALL]7select_expression,...8[INTO {OUTFILE | DUMPFILE} 'file_name' export_options]9[FROM table_references10...
骂归骂,事情还是得解决,时候我分析原因发现,发现有些表的数据量增长很快,对应SQL扫描了很多无效数据,导致SQL慢了下来,通过确认之后,这些大表都是一些流水、记录、日志类型数据,只需要保留1到3个月,此时需要对表做数据清理实现瘦身,一般都会想到用insert + delete的方式去清理。
(0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 (gcdb@localhost) 10:47:11 [mytest]> insert into t1(a) select 13; -- insert XXX select XXX 语法,MySQ独有 Query OK, 1 row affected (0.00 sec) Records: 1 Duplicates: 0 Warnings: 0 (gcdb@localhost) 10:53:34 [mytest]> select * ...