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PostgreSQL - how to quickly drop a user with existing privileges
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Doing: CREATE TABLE foo(bar SERIAL); ALTER TABLE foo OWNER TO postgres; CREATE USER testuser; GRANT ALL ON foo TO testuser; DROP USER testuser gave the error messages: ERROR: role "testuser" cannot be dropped because some objects depend...
Split comma-separated strings in a column into separate rows
...approach but modified according to Rich Scriven's comment,
Jaap's two data.table methods and two dplyr / tidyr approaches,
Ananda's splitstackshapesolution,
and two additional variants of Jaap's data.table methods.
Overall 8 different methods were benchmarked on 6 different sizes of data frames u...
Why are joins bad when considering scalability?
...ted comparison for a join is now much smaller and potentially pre-indexed.
Table partitions (helps with large data sets by spreading the load out to multiple disks, or limiting what might have been a table scan down to a partition scan)
OLAP (pre-computes results of certain kinds of queries/joins. I...
How do I find duplicate values in a table in Oracle?
...or a given column and the count of their occurrences in an Oracle database table?
13 Answers
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Splitting string into multiple rows in Oracle
...str(t.error, '[^,]+', 1, levels.column_value)) as error
from
temp t,
table(cast(multiset(select level from dual connect by level <= length (regexp_replace(t.error, '[^,]+')) + 1) as sys.OdciNumberList)) levels
order by name
EDIT:
Here is a simple (as in, "not in depth") explanation of t...
Oracle find a constraint
...stem generated constraint name. For instance, if we specify NOT NULL in a table declaration. Or indeed a primary or unique key. For example:
SQL> create table t23 (id number not null primary key)
2 /
Table created.
SQL> select constraint_name, constraint_type
2 from user_constraint...
MySQL 启动报错 Table \'mysql.plugin\' doesn\'t exist - 数据库(内核) -...
MySQL 启动报错 Table 'mysql.plugin' doesn't exist 启动报错： opt szy bin mysqld: Table 'mysql.plugin ' doesn 't exist141211 15:06:12 [ERROR] Can 't open t...启动报错：
/opt/szy/bin/mysqld: Table \'mysql.plugin\' doesn\'t exist
141211 15:06:12 [ERROR] Can\'t open the mysql.plug...
Mysql ibdata 丢失或损坏如何通过frm&ibd 恢复数据 - 爬虫/数据库 - 清...
...这个方法不能恢复你的数据。my.ini的设置为 innodb_file_per_table = 1。参考 http://blog.chinaunix.net/uid-24111901-id-2627876.html1、找回表结构，如果表结构没有丢失直接到下一步
a、先创建一个数据库，这个数据库必须是没有表和任何操作的...
Solutions for INSERT OR UPDATE on SQL Server
Assume a table structure of MyTable(KEY, datafield1, datafield2...) .
22 Answers
22
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Is there a naming convention for MySQL?
... this is not always possible. Think about how you would cope with a single table foo_bar that has columns foo_id and another_foo_id both of which reference the foo table foo_id column. You might want to consider how to deal with this. This is a bit of a corner case though!
Point 4 - Similar to Poin...