大约有 1,948 项符合查询结果（耗时：0.0108秒） [XML]
Laravel orderBy on a relationship
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If you use mysql strict mode, which is default in Laravel 5.4 ,f.ex you'll receive SQLSTATE[42000]: Syntax error or access violation: 1140 Mixing of GROUP columns ...
– Sabine
Feb 18 '17 at 15:15
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Computed / calculated / virtual / derived columns in PostgreSQL
...s defined in the SQL standard and implemented by some RDBMS including DB2, MySQL and Oracle. Nor the similar "computed columns" of SQL Server.
STORED generated columns are introduced with Postgres 12. Trivial example:
CREATE TABLE tbl (
int1 int
, int2 int
, product bigint GENERATED ALWAYS...
Why should I use document based database instead of relational database?
... my schema, I am constantly frustrated by having to maintain the schema in MySQL/SQLite. While I've not done too much with CouchDB yet, I do like how simple it is to evolve the schema during the RAD process.
A case where you might not want to use a non-relational database is when you have a lot of ...
SQLAlchemy: how to filter date field?
..., once it's DateTime or timestamp - it's usually finished with 00:00 (both MySQL & PostgreSQL do this). More generic solution is not to cast, but to set the date you are sending to it's .endOfDay() so you actually send 1988-01-17 23:59:59 to the database compare :)
– jave.w...
Difference between CLOB and BLOB from DB2 and Oracle Perspective?
...es, documents, other)
CLOB is for large text data (text)
Maximum size on MySQL 2GB
Maximum size on Oracle 128TB
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从源代码剖析Mahout推荐引擎 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...。
通过“策略模式”匹配不同的数据源，支持File, JDBC(MySQL, PostgreSQL), NoSQL(Cassandra, HBase, MongoDB)。
注：NoSQL的实现在mahout-integration-0.8.jar中。
数据格式支持2种：
GenericDataModel: 用户ID，物品ID，用户对物品的打分(UserID,ItemID,Pre...
HTTP authentication logout via PHP
...cookie, with the persistence of state stored on the server in some manner (mysql, sqlite, flatfile, etc). This will require all requests to be evaluated, for instance, with PHP.
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What is the Oracle equivalent of SQL Server's IsNull() function?
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+1: COALESCE is ANSI, supported by Postgres, MySQL... The only caveat is that it doesn't necessarily perform as fast as native syntax.
– OMG Ponies
Aug 19 '10 at 17:33
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getting date format m-d-Y H:i:s.u from milliseconds
....433818
10-29-2015 11:40:09.433818
Note that if you want to input into mysql, the time format needs to be:
format("Y-m-d H:i:s.u")
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mysqli or PDO - what are the pros and cons? [closed]
In our place we're split between using mysqli and PDO for stuff like prepared statements and transaction support. Some projects use one, some the other. There is little realistic likelihood of us ever moving to another RDBMS.
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