What is the CLOB data type

What are CLOBs (Character Large Objects)?

One of the biggest advantages of the data type CLOB is the possibility of Reading and editing operations to be carried out on the individual files. For example, database administrators can use application programs to compare, edit or merge the content of character large objects that have been fed in. A brief overview of the editing options follows:

  • SUBSTR allows users to extract character sequences from a CLOB
  • INSTR inserts cut strings elsewhere or in other CLOBs
  • COMPARE compares the values ​​of two CLOBs
  • APPEND connects two CLOBs with each other

There CLOBs save the documents completely with text or characters, their contents can be checked very carefully. Administrators can determine exactly whether content is duplicated or text parts overlap. If this is the case, the data sets can be linked in order to free up unnecessarily used storage space.

In addition, letters, digits, special characters and control characters can be saved as CLOB absolutely lossless: When saving, it is often important that all the information in a document really has to be saved, which is not a problem with this data format. For example, you can also save the meta information of a document together with the actual content as a CLOB. Most databases even support the representation of the Character Large Objects in a tree structure as well as the navigation and the finding of specific components.

To the Disadvantages this data type for storing huge amounts of characters counts that some databases not editing via the familiar SQL functions enable. Since the CLOBs store extremely large amounts of text, the execution of the standard functions would take a very long time. Here, however, at least the previously mentioned application commands SUBSTR, INSTR, COMPARE and APPEND are available as alternative options for replicating non-functional SQL operations. Another disadvantage of CLOBs: Relatively small pieces of data waste valuable storage space, since a firmly defined, segmented storage space is reserved for storage outside the database.