Basic query
View the current user:
show user
Query Table Information:
select * from table
View line width:
show linesize；
Set the line width:
set linesize 150；
Set Column Width:
col name format a8;
Cmd command on a modification of a SQL statement error:
c / wrong word / the correct word; write-change / execute SQL statements;
SQL statements can be placed operators:
If there is a null value, a value attached to him:
nvl (a, b) is null if a value that a = b; if! = Null then a = a.
ed Command + Enter:
The command to write on a local default notepad;
Remove duplicate records:
distinct, for all columns later.
Connector ||, cat:
Sql and sqlplus difference:
Dual：
Dummy table
One-way function of the character function
Change case:
Lower () to lowercase; upper () are converted to uppercase; initcap () initial capital letters.
Interception string:
Substr (a, b, c) from the a, the b 'c' as the start to take away.
Number of characters:
Length characters; lengthb number of bytes.
Note: not byte characters are not the same and, if the Chinese character, a Chinese character is a character, but is a two-byte characters.
It contains the string:
Instr (a, b) comprising a string of b.
filling:
Lpad ( "", n, "") left filled parentheses filling parameters for the filling in on that string, filling several, filled with what.
Rpad ( "", n, "") right padding.
Before and after removing the specified character:
Trim（）。
replace:
replace().
