Introduction to bi-sql wildcards

wildcard

The concept of wildcard is an important part of database language .

The important reason must be that you can guess , The data level of data warehouse is usually large , Many times we do data query , You can't guarantee the accuracy of your query conditions , Or we need fuzzy query to get a kind of data , Wildcards are useful in this case .

Compare with SQL,PowerBI There are few opportunities to use wildcards .

The fundamental reason lies in their different positioning .PowerBI Focus on the front-end display of data ,SQL It is the back-end data cleaning and storage .

SQL Wildcard category

wildcard	describe
%	Replace one or more characters
_	Replace a character
[ list ]	Scope of Supply
[^ list ]	Not in the scope of supply
[! list ]	Not in the scope of supply

notes ： The wildcard must be associated with LIKE Use it with .

Using examples

Case data ：

In the database of white tea machine , There is a name “TEST” The database of , There is a name “ Product list ” Case data for .

Example 1：

stay PowerBI Get the product table in [ Name of commodity ] Beginning with “ child ” All data for .

SELECT * FROM  Product list  WHERE  Name of commodity  LIKE N' child %'

give the result as follows ：

Example 2：

stay PowerBI Get the product table in [ Name of commodity ] It ends with “ pants ” All data for .

SELECT * FROM  Product list  WHERE  Name of commodity  LIKE N'% pants '

give the result as follows ：

Example 3：

stay PowerBI Get the product table in [ Name of commodity ] The middle contains “ son ” All data for .

SELECT * FROM  Product list  WHERE  Name of commodity  LIKE N'% son %'

give the result as follows ：

Example 4：

stay PowerBI Get the product table in [ Name of commodity ] The middle contains “ son ” And the number of characters is 3 All the data .

SELECT * FROM  Product list  WHERE  Name of commodity  LIKE N'_ son _'

give the result as follows ：

Example 5：

stay PowerBI Get the product table in [ Name of commodity ] It begins with “ mouth 、 Infant 、 child ” All data for .

SELECT * FROM  Product list  WHERE  Name of commodity  LIKE N'[ Oral infant child ]%'

give the result as follows ：

Example 6：

stay PowerBI Get the product table in [ Name of commodity ] Does not begin with “ mouth 、 Infant 、 child ” All data for .

SELECT * FROM  Product list  WHERE  Name of commodity  LIKE N'[^ Oral infant child ]%'

give the result as follows ：

This is white tea , One PowerBI Beginners .