Oracle FAQ 7

255. chartorowid (char)
Convert the char or varchar2 values that contain the rowid of the external signature method to the binary notation of the internal part, char must be an 18-character string containing the rowid of the external signature method.
Select name from bsempms where rowid = chartorowid ('aaaafzaabaaacp8aao ');
Name: leixue

256. Convert (char, dest_char_set, source_char_set)
Convert uploads the characters in the string char from the character set recognized by source_char_set to the character set recognized by dest_char_set.

Select convert ('grob', 'us7ascii ', 'we8hp') 'version' from pubs;
Conversion: Gross

257. hextoraw (char)
Converts a hexadecimal Char into a raw value.
Insert into bsempms (raw_column) Select hextoraw ('7d ') from test;

258. rawtohex (raw)
Convert the raw value to a char value that contains the hexadecimal format.
Select rawtohex (raw_column) 'version' from bsempms;
Conversion: 7d

259. rowidtochar (rowid)
Returns the value of a rowid to the varchar2 data type.
Select rowid from bsempms where rowidtochar (rowid) like '% br1aab % ';

260. to_multi_byte (char)
Convert single-character in Char to an equivalent multi-character.
Select to_multi_byte ('asfdfs') from test;

261. to_single_byte (char)
Converts multiple characters in a char string to an equivalent single-character string.
Select to_single_byte ('asfdfs') from test;

262. Translate using (Text Using {char_cs | nchar_cs })
Converts text into a data character set and a national character set according to the specified encoding method.
Text is to be written.
Using char_cs numeric character text is the data character set. The numeric data type is varchar2.
Using nchar_cs numeric character text is the data character set. The numeric data type is nvarchar2.
Create Table Test (char_col char (20), nchar_col nchar (20 ));
Insert into test values ('Hi, n' bye ');
Select * from test;

263. Dump (expr, return_format, start_position, length)
Returns a varchar2 value that contains the internal representation information, such as the number of data types and the number of characters. the result returned is the data source character set. The data type is returned based on the internal data type specified below:
Representative Data Type
0 varchar2
1 Number
8 long
12 Date
23 raw
24 long raw
69 rowid
96 char
106 msslabel
Retuen_format indicates the returned data value according to the base number below.
Return_format result
8x8
10 10 hexadecimal
16 hexadecimal
17 single character representation
If return_format is not specified, the return value is in hexadecimal format.
If the values 'start _ position' and 'length' are specified, the word 'length' starting from 'start _ position' will be returned. The default value is to return an integer.
Select dump ('abc', 1016) from test;
Select dump (ename, 8, 3, 2) 'example 'from EMP where name = 'ccbzzp ';

264. empty_ B | clob ()
Returns an empty lob locator, which is used to initialize the lob volume, or to insert or update the indicator to initialize the lob column, or leave it null.
Insert into Table1 values (empty_blob ());
Update Table1 set clob_col = empty_blob ();

265. bfilename ('Directory ', 'filename ')
Returns a bfile locator. The related binary lob physical files are stored in the file system of the server. directory refers to the domain name used to search the full name of a path in the file system of the server. filename refers to the file name of the server's file system.
Insert into file_tab values (bfilename ('lob _ dir', 'image1. gif '));

266. Greatest (expr, expr ,...)
Greatest returns the maximum number of rows.
Select greatest ('Harry ', 'harriot', 'harold') 'sample' from Table1;

267. Least (expr, expr ,...)
Least returns the minimum value of the number of rows.
Select least ('Harry ', 'harriot', 'harold') 'sample' from Table1;

268. nls_charset_decl_len (bytecnt, csid)
Returns the degree of parallelism of an nchar column.
Select nls_charset_decl_len (200, nls_charset_id ('ja16eefdfdf ') from Table1;

269. nls_charset_id (text)
Returns the number of NLS Character Set IDs corresponding to the NLS Character Set Name.
Select nls_charset_d ('jadfdffdf ') from Table1;

270. nls_charset_name (N)
Returns the NLS Character Set Name that corresponds to ID n.
Select nls_charset_name (2) from Table1;

271. nvl (expr1, expr2)
If expr1 is null, expr2 is returned. Otherwise, expr1.
Select name, nvl (to_char (Comm), 'not application') from Table1;

272. uid
Returns the integer used to identify the data before the unique criterion.
Select uid from Table1;

273. User
Returns the name of the Oracle database that was created before using the varchar2 data type.
Select User, uid from Table1;

274. userenv (option)
Returns the previous session information.
Option = 'isdba 'if it is a DBA role, it is true. Otherwise, it is false.
Option = 'language' returns the character set of the data source.
Option = 'sessionid' indicates the Pre-session identifier.
Option = 'entryid' returns a predictable speaker.
Option = 'lang ': return the ISO record of the speaker.
Option = 'instance' returns the previous example.
Select userenv ('language') from dual;

275. vsize (expr)
Returns the number of internal characters in expr.
Select name, vsize (name) from Table1;

276. deref (E)
Returns the object reference of object number E.
Select deref (C2) from Table1;

277. reftohex (r)
Convert the numeric value to hexadecimal.
Select reftohex (C2) from Table1;

278. make_ref (table, key, key ...)
By using the given token as the master token, we can create a reference for the fixed token pair to the row in the image.
Create Type T1 as object (a number, B number );
Create Table tb1 (C1 number, C2 number, primary key (C1, C2 ));
Create view V1 of T1 with object OID (A, B) as select * From tb1;
Select make_ref (V1, 1, 3) from pubs;

279. stddev (distinct | all X)
Stddev returns a set of row values.
Select stddev (salary) as example from employee;

280. Variance (distinct | all X)
Variance returns the variance of all values in a group of rows.
Select variance (salary) as example from employee;