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What's the difference between VARCHAR and CHAR?
What's the difference between VARCHAR and CHAR in MySQL?
14 Answers
14
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How to remove constraints from my MySQL table?
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Mysql has a special syntax for dropping foreign key constraints:
ALTER TABLE tbl_magazine_issue
DROP FOREIGN KEY FK_tbl_magazine_issue_mst_users
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Does MySQL ignore null values on unique constraints?
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Yes, MySQL allows multiple NULLs in a column with a unique constraint.
CREATE TABLE table1 (x INT NULL UNIQUE);
INSERT table1 VALUES (1);
INSERT table1 VALUES (1); -- Duplicate entry '1' for key 'x'
INSERT table1 VALUES (NULL);...
PHP prepend associative array with literal keys?
...hat contains the new key-value pair at the beginning of the array with the union operator +. The outcome is an entirely new array though and creating the new array has O(n) complexity.
The syntax is below.
$new_array = array('new_key' => 'value') + $original_array;
Note: Do not use array_merg...
那些曾被追捧的90后创业男神女神，还好吗？ - 资讯 - 清泛网 - 专注C/C++及内核技术
...右，距离1%还差不少。但不晓得安妮以及她的团队今后会如何去做，或许这样让人眼前一亮的作品再次出现要等很久，但我们却不得不承认，这次的1%亮了。
点评：鸡汤是这个时代最好的精神补品，但此前以漫画形式成功的案例...
MySQL - Make an existing Field Unique
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ALTER IGNORE TABLE mytbl ADD UNIQUE (columnName);
For MySQL 5.7.4 or later:
ALTER TABLE mytbl ADD UNIQUE (columnName);
As of MySQL 5.7.4, the IGNORE clause for ALTER TABLE is removed and
its use produces an error.
So, make sure to remove duplicate entries first as IGNO...
How many levels of pointers can we have?
...eclarators (in any combinations) modifying an
arithmetic, structure, union, or void type in a declaration
The upper limit is implementation specific.
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那些微信公众大号是如何赚钱的？ - 资讯 - 清泛网 - 专注C/C++及内核技术
那些微信公众大号是如何赚钱的？如今，微信公众号不仅是传递好文的平台，承载着万千运营者的兴趣和梦想，而且当粉丝量和文章阅读量高涨之后，随之而来的还有丰厚的经济效益。“你开公众号了吗？”不知从何时起，这个...
OnInitUpdate、OnUpdate、OnDraw与OnPaint - C/C++ - 清泛网 - 专注C/C++及内核技术
...情况下可能需要和框架直接发生作用，而在多视的情况下如何在视之间传递数据。
在使用菜单时大家会发现当一个菜单没有进行映射处理时为禁止状态，在多视的情况下菜单的状态和处理映射是和当前活动视相联系的，这...
MySQL “between” clause not inclusive?
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From the MySQL-manual:
This is equivalent to the expression
(min <= expr AND expr <= max)
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