Explain ACID rule of thumb for transactions.
A transaction must be:
1. Atomic - it is one unit of work and does not dependent on previous and following transactions.
2. Consistent - data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t.
3. Isolated - no transaction sees the intermediate results of the current transaction). 4. Durable - the values persist if the data had been committed even if the system crashes right after.
What does the Initial Catalog parameter define in the connection string?
Between Windows Authentication and SQL Server Authentication, which one is trusted and which one is untrusted?
Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
Let’s take a look at the differences between ADO Recordset and ADO.Net DataSet:
1. Table Collection: ADO Recordset provides the ability to navigate through a single table of information. That table would have been formed with a join of multiple tables and returning columns from multiple tables. ADO.NET DataSet is capable of holding instances of multiple tables. It has got a Table Collection, which holds multiple tables in it. If the tables are having a relation, then it can be manipulated on a Parent-Child relationship. It has the ability to support multiple tables with keys, constraints and interconnected relationships. With this ability the DataSet can be considered as a small, in-memory relational database cache.
2. Navigation: Navigation in ADO Recordset is based on the cursor mode. Even though it is specified to be a client-side Recordset, still the navigation pointer will move from one location to another on cursor model only. ADO.NET DataSet is an entirely offline, in-memory, and cache of data. All of its data is available all the time. At any time, we can retrieve any row or column, constraints or relation simply by accessing it either ordinarily or by retrieving it from a name-based collection.
3. Connectivity Model: The ADO Recordset was originally designed without the ability to operate in a disconnected environment. ADO.NET DataSet is specifically designed to be a disconnected in-memory database. ADO.NET DataSet follows a pure disconnected connectivity model and this gives it much more scalability and versatility in the amount of things it can do and how easily it can do that.
4. Marshalling and Serialization: In COM, through Marshalling
Default : The row the default version for the current DataRowState. For a DataRowState value of Added, Modified or Current, the default version is Current. For a DataRowState of Deleted, the version is Original. For a DataRowState value of Detached, the version is Proposed.
Original: The row contains its original values.
Proposed: The proposed values for the row. This row version exists during an edit operation on a row, or for a row that is not part of a DataRowCollection
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and password).
Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings. The connection string must be identical.
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