Oracle syntax and oracle syntax

Oracle syntax and oracle syntax

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Select * FROM Table Where ROWNUM <= 2 order by AgeUnitNo desc

ROWNUM <= 2 indicates that two pieces of data are queried.

Date

To_date () indicates the data that can be recognized by Oracle

Update talbe set A1 = to_date ('"+ model. Tstamp. ToString () +"', 'yyyy-MM-DD HH24: MI: ss ');

Auto-increment ID

1. Oracle does not have the auto-increment attribute. Therefore, you need to customize a SEQUENCE.

Create sequence emp_sequence
Increment by 1 -- add several
Start with 1 -- count from 1
NOMAXVALUE -- do not set the maximum value
NOCYCLE -- always accumulate without repeating
NOCACHE -- do not create a buffer

2. Create a trigger

Create or replace trigger emp BEFORE
Insert ON Table FOR EACH ROW
Begin
Select emp_Sequence.nextval into: New. TableID from Dual;
End;

To be supplemented

Basic oracle syntax

Query statement-select * from table;
Select * from table where Condition 1 = value and condition 2 = value;
Select * from table where id in (select id from table); two table associations
Select a. a, B. B, c. c from table1 a, table2 B, table3 c where a. id1 = B. id2;
Insert statement-insert into table (Field 1, Field 2, Field 3 ,......)
Values (value 1, value 2, value 3 ,......);
Update statement-update table name set value where = id = 1;

Add column statement-alter table name
Add (column name 1 Type 1, column name 2 type 2, column name 3 type 3 ,......);

Query 20 random records-select * from (select * from emp order by dbms_random.value) where rownum <= 10;
Alter column type-alter table name
Modify (column name 1 Type 1, column name 2 type 2, column name 3 type 3 ,......);
Delete column statement-alter table name
Drop column name s;
Display query time-set timing on;

Delete table statement-deltet table name;

Clear table data-truncate table name;

Alter table emp rename column comm TO newa;

Set query (no duplicates): select * from table_name union
Select * from table_name;
Set query (repeated): select * from table_name union all
Select * from table_name;
Query the difference set: select * from table_name minus
Select * from table_name;

--------------------------------------------------------------------------------
Run the script-start d: \ file name. SQL;

Edit script-edit d: \ file name. SQL;

Save As script-spool d: \ file. SQL;
Select * from emp;
Spool off;

Page display-set pagesize page number;

Display the number of rows-set linesize the number of rows;

Create user-create user username identified by password (requires SYS/SYSTEM permission to create a user)
Grant permissions-grant resource to user name; (Table creation permission)
Grant query permission-grant select on emp to user name;
Grant the modification permission-grant update on emp to the user name;
Grant all access permissions-grant all on emp to user name;
----------------------------------------------------- ...... The remaining full text>

| What is represented in Oracle syntax?

Connector. For example, select 'this is '| 'connector' from dual
The result is as follows:
Is to splice two pieces of data.
Hope to adopt