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Do I need to create indexes on foreign keys on Oracle?
I have a table A and a table B . A has a foreign key to B on B 's primary key, B_ID .
7 Answers
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select into in mysql
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Use the CREATE TABLE SELECT syntax.
http://dev.mysql.com/doc/refman/5.0/en/create-table-select.html
CREATE TABLE new_tbl SELECT * FROM orig_tbl;
share
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App Inventor 2 SQLite 拓展：超流行兼容主流SQL语法的迷你本地数据库引擎...
...数据表
创建一个测试数据表，sql如下：
CREATE TABLE users (
id INTEGER PRIMARY KEY,
name TEXT,
age INTEGER);
数据表信息
这时，可以查看一下表信息：
插入数据
往 users 表中插入...
SQL JOIN - WHERE clause vs. ON clause
...r join has taken place.
b. ON clause - Before joining. Records (from right table) will be filtered before joining. This may end up as null in the result (since OUTER join).
Example: Consider the below tables:
1. documents:
| id | name |
--------|-------------|
| 1 ...
When to use “ON UPDATE CASCADE”
... ON UPDATE CASCADE would allow you to change the primary key value and any tables that have foreign key references to the value will be changed accordingly.
In reference to #4, if you change the child ID to something that doesn't exist in the parent table (and you have referential integrity), you s...
Log all queries in mysql
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Is it possible to log queries over 1 particuarl db / table only?
– Temujin
Aug 4 '12 at 16:08
2
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Real life example, when to use OUTER / CROSS APPLY in SQL
...ORDER BY pr.name) pa
ORDER BY pr.name,
pa.name
2) Calling a Table Valued Function for each row in the outer query
SELECT *
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle)
3) Reusing a column alias
SELECT number,
doubled_number,
...
Import CSV to SQLite
I'm trying to import a csv file to an SQLite table.
10 Answers
10
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CSS center text (horizontally and vertically) inside a div block
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Since they tend to be hacks or adding complicated divs... I usually use a table with a single cell to do it... to make it as simple as possible.
Update for 2020:
Unless you need make it work on earlier browsers such as Internet Explorer 10, you can use flexbox. It is widely supported by all cur...
Transaction isolation levels relation with locks on table
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I want to understand the lock each transaction isolation takes on the table
For example, you have 3 concurrent processes A, B and C. A starts a transaction, writes data and commit/rollback (depending on results). B just executes a SELECT statement to read data. C reads and updates data. All t...