How to empty my destination table before inserting new records in SSIS?
Put your delete statement in an Execute SQL Task. Then make it the first component of your flow. The component looks something like this:
relational-database
Closest equivalent to SQLAlchemy for Java/Scala [closed]
One of the notable things about SQLAlchemy is that it makes tables first class objects. Thus the core API is really written around table objects, and the API therefore is essentially relational in nature. Thus at this level even if the API is OO, it is essentially reflecting RDBMS objects or functions such as Tables, … Read more
Will multiple calls to `now()` in a single PostgreSQL query always give the same result?
The documentation says about now(): now() is a traditional PostgreSQL equivalent to transaction_timestamp() And about transaction_timestamp(): These SQL-standard functions all return values based on the start time of the current transaction So within one SQL statement, now() will always return the same value.
Can one make a relational database using MongoDB?
The idea behind MongoDB is to eliminate (or at least minimize) relational data. Have you considered just embedding the attendance data directly into each student record? This is actually the preferred design pattern for MongoDB and can result in much better performance and scalability. If you truly need highly relational and normalized data, you might … Read more
Decomposing a relation into BCNF
Although the question is old, the other questions/answers don’t seem to provide a very clear step-by-step general answer on determining and decomposing relations to BCNF. 1. Determine BCNF: For relation R to be in BCNF, all the functional dependencies (FDs) that hold in R need to satisfy property that the determinants X are all superkeys … Read more
Is MongoDB a valid alternative to relational db + lucene? [closed]
Technically you can do full text search with MongoDB, but you’re missing out on a lot that a full text search provider has to offer. I love MongoDB, but I’d couple it with a full text search provider (such as Lucene or Sphinx) if time to implementation is at all a concern. I think MongoDB’s … Read more
SQL semantics for “FOR UPDATE” & “JOIN”
You’ve got it correct. In a “SELECT FOR UPDATE” with a JOIN, any rows that contribute to the returned rows will be locked. You can change this behavior by adding an “OF table_a” to the “FOR UPDATE” so that only the rows from table_a will be locked. You can read more about this in the … Read more
Query the contents of stored procedures on SQL Server
SELECT OBJECT_NAME(object_id), definition FROM sys.sql_modules WHERE objectproperty(object_id,’IsProcedure’) = 1 AND definition like ‘%Foo%’
Postgresql delete multiple rows from multiple tables
Arranging proper cascading deletes is wise and is usually the correct solution to this. For certain special cases, there is another solution to this that can be relevant. If you need to perform multiple deletes based on a common set of data you can use Common Table Expressions (CTE). It’s hard to come up with … Read more
Why are relational databases having scalability issues?
Imagine two different kinds of crossroads. One has traffic lights or police officers regulating traffic, motion on the crossroad is at limited speed, and there’s a watchdog registering precisely what car drove on the crossroad at what time precisely, and what direction it went. The other has none of that and everyone who arrives at … Read more