SQL Server Learning Series-Gets the number of occurrences of a character in a string and the subscript at which a character appears

DECLARE @Str NVARCHAR( -)= '1_bb_cc_dd_aa_ee_yy_ww_hh_gg'--//1. Gets the number of times an underscore appears in a stringSELECT LEN(@Str)- LEN(REPLACE(@Str,'_',"'))--//2. Get the subscript where the underline appearsIF  EXISTS(SELECT *  fromSys.objectsWHERE object_id = object_id(N'[dbo]. [Indexnumofstr]') andTypeinch(N'FN'N'IF'N'TF'N'FS'N'FT'))    DROP FUNCTION [dbo]. IndexnumofstrGOCREATE FUNCTIONdbo. Indexnumofstr (@Str     NVARCHAR( -),--string    @charStr NVARCHAR( -),--the character to query    @num     INT                    --The first few occurrences)RETURNS INT  asBEGIN    DECLARE @posIndex INT = 0        --the location that appears    DECLARE @i INT = 0                --Number of lookups     while @i < @num    BEGIN        SET @i = @i + 1        SET @posIndex = CHARINDEX(@charStr,@Str,@posIndex + 1)        IF @posIndex = 0        BEGIN            RETURN 0        END    END    RETURN @posIndexENDGO--//test ResultsSELECTDbo. INDEXNUMOFSTR (@Str,'_',Ten)

SQL Server Learning Series-Gets the number of occurrences of a character in a string and the subscript at which a character appears