Question

It seems vsize() and length() return the same results. Does anyone know of a practical example of when to use vsize instead of length?

select vsize(object_name), length(object_name) from user_objects 

Result:

/468ba408_LDAPHelper    20  20 /de807749_LDAPHelper    20  20 A4201_A4201_UK  14  14 A4201_PGM_FK_I  14  14 A4201_PHC_FK_I  14  14 

Answer 1

Well, Length() takes a character argument (CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB) whereas VSize() takes just about any data type, so if you pass Length() a noncharacter data type there has to be an implicit conversion.

Length is also sensitive to to character sets.

drop table daa_test; create table daa_test as select sysdate dt from dual; alter session set nls_date_format = 'YYYY-MM-DD'; select vsize(dt)  from daa_test; select length(dt) from daa_test; alter session set nls_date_format = 'YYYY-MM-DD HH24:mi:ss'; select vsize(dt)  from daa_test; select length(dt) from daa_test; 

… giving …

drop table daa_test succeeded. create table succeeded. alter session set succeeded. VSIZE(DT)               ----------------------  7                        1 rows selected  LENGTH(DT)              ----------------------  10                       1 rows selected  alter session set succeeded. VSIZE(DT)               ----------------------  7                        1 rows selected  LENGTH(DT)              ----------------------  19                       1 rows selected 

VSize is really of use IMHO in understanding internal storage requirements of data.