.NET/ASP.NET/C#/VB.NET PDF Document SDK

com) covers it in some detail Session: A session is a logical entity that exists in the instance It is your session state, or a collection of data structures in memory that represents your unique session It is what would come first to most people s minds when thinking of a database connection It is your session on the server, where you execute SQL, commit transactions, and run stored procedures..

ssrs code 128 barcode font, ssrs code 39, ssrs fixed data matrix, winforms pdf 417 reader, winforms qr code reader, winforms upc-a reader, c# remove text from pdf, itextsharp replace text in pdf c#, winforms ean 13 reader, c# remove text from pdf,

We can use SQL*Plus to see connections and sessions in action, and also to recognize that it could be a very common thing indeed for a connection to have more than one session. We ll simply use the

A relational database table is essentially a two-dimensional matrix with rows (records) and columns (fields). A primary key is a column that uniquely identifies each row, and that means you cannot store the same value in a primary key column of any two records (so it is also a unique key). The primary key is usually a single numeric column, but it can also be composed as a set of columns, in which case it is called a composite primary key. Tables can be linked or related to one another using relationships. To set up a relationship, you need foreign keys, which are columns that store primary key values in a host table. For instance, in a one-to-one relationship, a record in table A can be associated with a record in table B by A containing a foreign key to B s primary key column, or vice versa, or both, depending on the navigability of the relationship. A one-to-one relationship is rare because it makes more sense to merge the two tables, unless the foreign key is allowed to be null. On the other hand, one-to-many (1..*) relationships are ubiquitous, allowing records in table A to be associated with multiple records in table B. For instance, a Customers table is likely to be associated with an Orders table this way, allowing each customer to have multiple orders. This can be modeled by storing a foreign key in Orders that refers to a Customers primary key. By moving two (or more) foreign keys in a separate so-called association table, we obtain a many-to-many relationship between those tables. Referential integrity refers to the fact that only valid primary key values are allowed in a foreign key column.

AUTOTRACE command and discover that we have two sessions! Over a single connection, using a single process, we ll establish two sessions. Here is the first: ops$tkyte%ORA11GR2> select username, sid, serial#, server, paddr, status 2 from v$session 3 where username = USER 4 / USERNAME SID SERIAL# SERVER PADDR STATUS --------- ---------- ---------- --------- -------- -------OPS$TKYTE 49 225 DEDICATED 32BC2B84 ACTIVE Now, that shows right now that we have one session: a single dedicated server connected session. The PADDR column is the address of our sole dedicated server process. Next, we turn on AUTOTRACE to see the statistics of statements we execute in SQL*Plus: ops$tkyte%ORA11GR2> set autotrace on statistics ops$tkyte%ORA11GR2> select username, sid, serial#, server, paddr, status 2 from v$session 3 where username = USER 4 / USERNAME SID SERIAL# SERVER PADDR --------- ---------- ---------- --------- -------OPS$TKYTE 30 5476 DEDICATED 32BC2B84 OPS$TKYTE 49 225 DEDICATED 32BC2B84 STATUS -------INACTIVE ACTIVE

Statistics ---------------------------------------------------------0 recursive calls 0 db block gets 0 consistent gets 0 physical reads 0 redo size 831 bytes sent via SQL*Net to client 419 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 2 rows processed ops$tkyte%ORA11GR2> set autotrace off In doing so, we now have two sessions, but both are using the same single dedicated server process, as evidenced by them both having the same PADDR value. We can confirm in the operating system that no new processes were created and that we are using a single process a single connection for both sessions. Note that one of the sessions (the original session) is ACTIVE. That makes sense: it is running the query to show this information, so of course it is active. But that INACTIVE session what is that one for That is the AUTOTRACE session. Its job is to watch our real session and report on what it does. When we enable AUTOTRACE in SQL*Plus, SQL*Plus will perform the following actions when we execute DML operations (INSERT, UPDATE, DELETE, SELECT, and MERGE):

Table 16-1 shows some of the most common database engines, all of which can be used from F# and .NET.