C # Normal encounter problems "4"

1. Parametric notation of like in fuzzy query

String keyword= "value"; To blur a matching value

Error Demonstration:　　

SQL: string strsql= "select * from [Table] where [Field] like% @Field%";

Parameter: system.data.sqlclient.sqlparameter[] parms = new[] {

New System.Data.SqlClient.SqlParameter ("@Field", system.data.sqldbtype.varchar,400)
};
Parms[0]. Value = KeyWord;

output: the arguments that are output by ADO SQL statement or the literal select * from [Table] where [Field] like% @Field% SQL statement error

Solution (1):

　　　　　　sql: string strsql= "select * from [Table] where [Field] like '% ' +@Field+ '% ' "

　　　　　This way, ADO can input the parameters correctly.

Solution (2):

　　　　　　sql: string strsql= "select * from [Table] where [Field] like @Field";　　　　　　

Parameter: system.data.sqlclient.sqlparameter[] parms = new[] {

New System.Data.SqlClient.SqlParameter ("@Field", system.data.sqldbtype.varchar,400)
};
Parms[0]. Value = "%" +keyword +"%";

Analysis:

The like statement that we expect to finally transfer to the database should be: SELECT * FROM [Table] like [Field] like '%value% ' ;

Direct% @Field%, contaminated with ADO parameter marked @ symbol resulting in incorrect substitution of parameters;

Method A string concatenation in the SQL statement to get a value such as '%value% '; Note: The strings in the SQL statement are quoted as the starting character of the string, and the string is stitched in SQL Server with the + sign. so '%value% ' equals '% ' +value '% ',

Method Two add the fuzzy match character directly in the assignment statement;

　　　　　　

C # Normal encounter problems "4"