大约有 3,551 项符合查询结果（耗时：0.0243秒） [XML]
ActiveRecord: List columns in table from console
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If you are comfortable with SQL commands, you can enter your app's folder and run rails db, which is a brief form of rails dbconsole. It will enter the shell of your database, whether it is sqlite or mysql.
Then, you can query the table columns using...
ALTER TABLE to add a composite primary key
...table you will get an error when trying to drop it. In some versions of mysql the error message there was malformed (as of 5.5.17, this error message is still
alter table parent drop column id;
ERROR 1025 (HY000): Error on rename of
'./test/#sql-a04_b' to './test/parent' (errno: 150).
If you wa...
Querying data by joining two tables in two database on different servers
...ID
Once the link is established, you can also use OPENQUERY to execute a SQL statement on the remote server and transfer only the data back to you. This can be a bit faster, and it will let the remote server optimize your query. If you cache the data in a temporary (or in-memory) table on DB1 in...
Why use a READ UNCOMMITTED isolation level?
... Oracle has "snapshot" by default since I know it, probably decades before Sql Server introduced it. I was quite disappointed when starting with SQL Server and I found out that all concurrency problems were solved using "primitive" locking mechanisms. Never saw "Read uncommitted" in Oracle. And the ...
Get the Query Executed in Laravel 3/4
How can I retrieve the raw executed SQL query in Laravel 3/4 using Laravel Query Builder or Eloquent ORM?
20 Answers
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How can I temporarily disable a foreign key constraint in MySQL?
Is it possible to temporarily disable constraints in MySQL?
10 Answers
10
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How do I get SUM function in MySQL to return '0' if no values are found?
Say I have a simple function in MySQL:
4 Answers
4
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How to remove a column from an existing table?
...n do this by querying system tables or using third party tools such as ApexSQL Search (free) or Red Gate Dependency tracker (premium but more features). There a whole thread on foreign keys here
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Laravel Eloquent: How to get only certain columns from joined tables
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I tried this and it shows an error SQLSTATE[42S22]: Column not found and it's SQL doesn't include the table in the with. The sql that it appears on the error is "SELECT fk_table.column1 FROM main_table".
– Michel Ayres
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LINQ To Entities does not recognize the method Last. Really?
...n comes down to the fact that eventually it has to translate that query to SQL and SQL has a SELECT TOP (in T-SQL) but not a SELECT BOTTOM (no such thing).
There is an easy way around it though, just order descending and then do a First(), which is what you did.
EDIT:
Other providers will possibly...