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“INSERT IGNORE” vs “INSERT … ON DUPLICATE KEY UPDATE”
...ut the values you insert don't map to a partition.
If you use REPLACE, MySQL actually does a DELETE followed by an INSERT internally, which has some unexpected side effects:
A new auto-increment ID is allocated.
Dependent rows with foreign keys may be deleted (if you use cascading foreign keys...
Checking for an empty field with MySQL
... and there's one record with null hotline but it doesn't match.I'm using MySQL 5.6
– Scott Chu
Apr 15 '16 at 10:16
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Handling warning for possible multiple enumeration of IEnumerable
...oom for too many assumptions. Do you really want someone to pass a LINQ to SQL query to this method, only for you to enumerate it twice (getting potentially different results each time?)
The semantic missing here is that a caller, who perhaps doesn't take time to read the details of the method, may...
Adding multiple columns AFTER a specific column in MySQL
...mitted in a single ALTER TABLE statement, separated by commas. This is a MySQL extension to standard SQL, which permits only one of each clause per ALTER TABLE statement.
– informatik01
May 1 '19 at 13:21
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How to move columns in a MySQL table?
Currently I am having the following MySQL table: Employees (empID, empName, department);
4 Answers
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What is SELF JOIN and when would you use it? [duplicate]
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SQL self-join simply is a normal join which is used to join a table to itself.
Example:
Select *
FROM Table t1, Table t2
WHERE t1.Id = t2.ID
share...
MySQL Workbench: How to keep the connection alive
Error Code: 2013. Lost connection to MySQL server during query
9 Answers
9
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Rails: select unique values from a column
...iq.pluck(:rating) is the most efficient way of doing this - this generates SQL which use SELECT DISTINCT rather than applying .uniq to an array
– Mikey
Jun 19 '13 at 15:38
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“互联网卖菜”没那么简单 创业者不要盲目跟风 - 资讯 - 清泛网 - 专注C/C+...
...的出发点是什么？便宜，吃的放心是最多的答案，但问及如何去做，多数人还是茫然。很多人都有这样的经历，每次去超市菜场总会暗骂商贩们把菜价喊得这么高，而且全部商贩统一口径不降价，第一反应想到的就是人工成本高...
How to map calculated properties with JPA and Hibernate
...ntioned, @Formula is perfect for this when using Hibernate. You can use an SQL fragment:
@Formula("PRICE*1.155")
private float finalPrice;
Or even complex queries on other tables:
@Formula("(select min(o.creation_date) from Orders o where o.customer_id = id)")
private Date firstOrderDate;
Wher...