Predicates, Expressions and Expression Trees

Question

User842257015 posted

Hi All,

I recently went through to learn repository based design to access data layer. would you someone help me what exactly below keyword contribution and when we use this approach(Performance)

• Predicates
• Expressions
• Expression Trees

  

Thanks,

Answer 1

User1400794712 posted

Hi jayakumarvinayagam,

Predicates:

Is an expression that evaluates to TRUE, FALSE, or UNKNOWN. Predicates are used in the search condition of WHERE clauses and HAVING clauses, the join conditions of FROM clauses, and other constructs where a Boolean value is required.

CONTAINS, FREETEXT, IS NULL/IS NOT NULL, In, Exists, Between, Like, All, any...

https://www.c-sharpcorner.com/UploadFile/rohatash/predicates-in-sql-server-2012/

https://docs.microsoft.com/en-us/sql/t-sql/queries/predicates

Expressions:

Is a combination of symbols and operators that the SQL Server Database Engine evaluates to obtain a single data value. Simple expressions can be a single constant, variable, column, or scalar function. Operators can be used to join two or more simple expressions into a complex expression.

http://www.tutorialsteacher.com/linq/linq-expression

Expression Tree:

Expression tree as name suggests is nothing but expressions arranged in a tree-like data structure.

http://www.tutorialsteacher.com/linq/expression-tree

Best Regards,

Daisy