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I see the term LOB used often when describing data types in columns of tables. What is it an acronym of, and why is this data object important?

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2 Answers 2

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“LOB” is short for “large object”.

In relational databases, data are typically stored in blocks of a fixed size to allow efficient interaction with storage.

Now if a value comes close to the size of a block or exceeds it, there is an obvious problem storing it in a table column. Such values are typically called LOBs, and different techniques have been proposed and used to store them, which typically involve splitting up the large value and storing it in more than one block.

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Oracle Database

Oracle Database SQL Language Reference, 12c Release 2 (12.2)

2.1 Data Types

2.1.1.6 Large Object (LOB) Data Types

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The built-in LOB data types BLOB, CLOB, and NCLOB (stored internally) and BFILE (stored externally) can store large and unstructured data such as text, image, video, and spatial data.

SQL Server

In SQL Server, LOB data types include xml, varbinary(max), and varchar(max) as mentioned in the documentation. The main distinguishing factor is the values may be stored separately from the row in LOB pages (a.k.a. blocks).

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