FuncEQ the same function as the equality comparison in SQL Builder function limitations SQLWhereLanguageDef.
Parameters GetFunction
GetFunction accepts the first argument type of a function funcEQ, and then takes 2 objects to compare them with each other. The first sent a description of the variable (Variable Definition), which will determine the objects to сравнения; and the second parameter is the object that will be compared.
Exception is type bool: langdef.GetFunction(langdef.funcEQ, new VariableDef(langdef.BoolType, "SomeBoolFlag")) will work without specifying the second parameter (the default will be compared with true).
Check for null should be carried out with FuncIsNull, when you try to check anything on null with FuncEQ will receive an exception Object reference not set to an instance of an object.
Example usage
For example, you want to subtract all the Loans specific Customer.
The SQL statement would look as follows:
SELECT * FROM Кредит WHERE Клиент = '{ID}'@@
Где {ID} - [Primary-keys-objects|первичный ключ) искомого `Клиента`
Клиент клиент = new Клиент();
SQLWhereLanguageDef langdef = SQLWhereLanguageDef.LanguageDef;
Function lf = langdef.GetFunction(langdef.funcEQ, new VariableDef(langdef.GuidType, Information.ExtractPropertyPath<Кредит>(x => x.Клиент)), клиент.__PrimaryKey);
Features string comparison
The fact that MS SQL Sever follows the standard ANSI 92 SQL in regard to string comparisons.
To determine whether strings of unequal length, especially on the right side the shorter string adds spaces, so the string lengths become equal.
Then the symbols in the first string are compared with characters of the second with regard to their location. If not equal at least one pair, the strings are considered unequal.
This applies to comparisons such as WHERE strfield = ‘…’, or HAVING strfield=’…’, or strfield IN (‘…’, ‘…’, …). In these cases, the string ‘abc’ and ‘abc’ are considered equal.
The exception is the operator LIKE (WHERE strfield LIKE ‘…’), for it is the string ‘abc’ and ‘abc’ is different, therefore, to impose restrictions on the string, you should use the function funcLike.