Oracle Select Statement

Method 1 delete yourtable where [id] not in (select max ([id]) from yourtable group by (name + value) b on a.id = b.id where b.id ...

Oracle defines a BLOB field for storing binary data, but this field does not hold true binary data, can only Gencun a pointer to the word, and then places the data in the LOB segment of Oracle to which the pointer points, and the LOB segment is part of the database's internal table. 　　Therefore, before manipulating an Oracle blob, the pointer (the locator) must be obtained before the BLOB data can be read and written. How do I get a blob pointer in a table? You can insert an empty B in a table using the INSERT statement first ...

One of the key decisions that companies that perform large data [note] projects face is which database to use, SQL or NoSQL? SQL has impressive performance, a huge installation base, and NoSQL is gaining considerable revenue and has many supporters. 　　Let's take a look at the views of two experts on this issue. Experts· VOLTDB's chief technology officer, Ryan Betts, says that SQL has won widespread deployments of large companies, and that big data is another area that it can support. Couch ...

As an outstanding representative of the Object relational database, Oracle is undoubtedly the most powerful. Whether it's the size of the database, the support of multimedia data types, the parallelism of SQL operations replication, or the security services, Oracle is much stronger than Sybase, Informix, Added to the latest version of the Oracle8.0.4 is to enhance the characteristics of this, but also introduced a number of new features, such as: Data partitioning (partitioning), Object-relational technology (objects relational T ...

We want to do not only write SQL, but also to do a good performance of the SQL, the following for the author to learn, extract, and summarized part of the information to share with you! (1) Select the most efficient table name order (valid only in the Rule-based optimizer): The ORACLE parser processes the table names in the FROM clause in Right-to-left order, and the last table in the FROM clause (the underlying table driving tables) is processed first, In the case where multiple tables are included in the FROM clause, you must select the table with the least number of records as the underlying table. If...

SQL statement for querying and deleting duplicate records (i) For example, there is a field "name" in Table A, and the "name" value may be the same between different records, and now you need to query between the records in the table, the "name" value has duplicates, and select name, Count (*) from-a group by name has count (*) > 1 as ...

SQL is the standard computer language used to access and process databases. What is SQL? SQL refers to Structured Query language SQL gives us the ability to access database SQL is an ANSI standard computer language editor Note: ANSI, United States national standardization Organization SQL What can you do? SQL database-oriented query SQL can retrieve data from a database SQL can insert new records in a database SQL updatable database can be deleted from the database SQL to delete records SQL can create New ...

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Big data is changing the IT world completely. So, what kind of data can be discussed? According to IDC, global data will increase 50 times times over the next decade. In 2011 alone, we will see large data creation of 1.8ZB (i.e. 1.8 trillion GB). This is equivalent to every American writing 3 tweets a minute, and still writing for 26,976 years. Over the next decade, the number of servers managing the Data warehouse will increase by 10 times times to cater for 50 times times larger data growth. There is no doubt that large data will challenge the enterprise's storage architecture and data ...

Large data will challenge the enterprise's storage architecture and data center infrastructure, and will trigger the ripple effect of cloud computing, data Warehouse, data mining, business intelligence and so on. In 2011, companies will use more TB (1TB=1000GB) Datasets for business intelligence and Business Analytics, and by 2020 global data usage is expected to rise 44 times-fold to 35.2ZB (1zb=10 billion TB). The challenges of large data for the vast number of data information, how the complex application of these data into the current data warehousing, business intelligence and data analysis technology ...