Null memory space

Fields from super types are first, 4 byte aligned. Null means 0. There is usually one place null defined in memory. Whenever one points to it using a programming language. Everything points to same place. It means only one 4 byte memory is consumed for NULL. Then whatever points to it does not consume any more memory. JAVA must have defined it similarly. It is not possible to point to nothing ofc. You have to point to something. But we define a common nothing and everything points to it consume only that space.

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Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Java - Does null variable require space in memory Ask Question. Asked 11 years, 10 months ago. Active 2 years, 1 month ago. Viewed 32k times. Improve this question. You can also check the Column Set value in more readable format by clicking on the XML blue value which will be displayed in separate window as the below:. The result will show you that, the single update statement we performed to that employee Column Set column is reflected on the Sparse Columns as follows:.

The Column Set overrides the maximum number of Sparse Columns per each table, which is columns for each table. The Column Set can contain up to 30, Sparse Columns in your table. However, no more than columns can be returned in the result set at the same time and in the XML Column Set result.

Combining it with the filtered indexes will result in a performance enhancement to your queries and smaller non-clustered indexes.

Together with the Column Set, Sparse Columns can be retrieved and modified in one shot, displayed in XML format and extends the number of columns per table limitation. Be careful when you use these features; as it is a double-edged sword; if you test it well and make sure that it will suit your case, you will get the best performance, otherwise it may cause performance degradation and consume your storage. FROM sys. Trailing nulls.

All consecutive NULLs at the end of the row are stored in one byte. Unless basic compression is enabled, then every NULL uses a byte again. Row overhead. Every row has overhead that depend on the columns and configuration. The skinnier the table, the more the row overhead uses up the space, so the percent used by a NULL will fluctuate.

Block overhead. This depends on the number of rows, settings like PCTFREE , if previous rows were deleted, when the table was last re-organized, block size, etc. Segment overhead. Space is allocated as chunks of extents. Extent management can use a default algorithm which I think allocates in chunks of 1MB up to 64MB or it can be any custom value.

This overhead becomes less relevant depending on the amount of data. It's possible a tablespace is set to a huge uniform extent size, such as 10GB, which will probably waste a lot of space regardless of the column values.

Alternative Representations? Asking about alternative representations of NULLs brings to mind four kinds of people: Hopelessly theoretical people who complain about violating the relational model and propose using obscure tools instead of the ones that have been working fine for decades.

Data architects who think a ginormous Entity-Attribute-Value table is always the answer. Stackoverflow users who read too much into questions. So feel free to add information on the background behind this question if I'm way off! Improve this answer. Jon Heller Jon Heller I have this table where columns can either have value or be NULL. Is there a way to find that information?

Find what? Are you looking for the NULL space used by a specific table at a specific point in time? One way to do that is to count all the NULLs and that's the number of bytes used to store the size of an empty column. Nice answer! My guess is that the question was asked because of HWM issues. In SQL Server non sparse columns, a bit of null bitmap mask is required to store the value of null. Tags: Correct use , null , server , Space occupation , sql. Solution Learning example of stored procedure for point acquisition and consumption SQL multi table row column transfer and cascade row column transfer example code Application examples of SQL time format output and convert function.