Oracle

Strange, no specific table structure information found Sql> describe dual;Name Type Nullable Default Comments----- ----------- -------- ------- --------DUMMY VARCHAR2 (1) YSql> SELECT * from dual;DUMMY-----XPurpose of the 2.DUAL tableDual is an

Ii. Transactions and LocksWhen performing transactional operations (DML statements), Oracle locks the table on which it is acting, preventing other users from modifying the structure of the table. This is very important for our users.III. Submission

Oracle has id,a column to how to read the non-duplicate value of the slaughter, and with the ID to sort, please help?Solution:ID | A1 | X2 | Y3 | XNon-repeating value of column A: x, yBut when you sort by ID, the ID of X applies 1 or 3.Therefore,

1,nvl2 (a,b,c) --expression 1 is not NULL, returns expression 2, or null. Returns an expression of 3. Expression 2 is different from the expression 3 type, and expression 3 is converted to the type of expression 2.2,nvl (expression 1, Expression 2)--

Transferred from: http://blog.sina.com.cn/s/blog_6bccf0360101hzsh.htmlWhat is the role of 1.spool?Spool's role can be described in a sentence: in Sqlplus to save or print query results.2.spool syntax and usage examples at Oracle 9i, 10g, and

1, query can restore the point in timeSELECT * from V$sql where sql_text like '%update map_optcbl_point_70 set shape% '2. Data recovery to a new table, based on timestampCREATE TABLE newtable as SELECT * from oldtable as of timestamp to_timestamp ('

basic Syntax Multi-table QueryThe Cartesian product is implemented in SQL as a cross join. All connections will be made by Mr Sir as a temporary Cartesian product table. The Cartesian product is a concept in relational algebra that represents the

Delete duplicate records. Because data is manually input, duplicate data is often generated, and redundant data needs to be deleted. Create a test table: CREATE TABLE dupes( id integer, name varchar(10));INSERT INTO dupes VALUES(1,

Convert null values to actual valuesCreate a test table: Create or replace view v asselect null as c1, null as c2, '1' AS c3, null as c4, '2' AS c5 FROM dualUNION allselect null as c1, null as c2, null as c3, '3' AS c4, '2' AS c5 FROM dual; SELECT *

Convert a null value to an actual value. Create a test table: Create or replace view v asselect null as c1, null as c2, '1' AS c3, null as c4, '2' AS c5 FROM dualUNION allselect null as c1, null as c2, null as c3, '3' AS c4, '2' AS c5 FROM dual;

Oracle tablespace operations, oracle tablespace-- View the tablespace SELECT tablespace_name, file_id, file_name, round (bytes/(1024*1024), 0) | 'M' total_spaceFROM dba_data_filesORDER BY tablespace_name; -- create tablespace testlogging datafile

Oracle 11g Release 2 Basic login operations after new installation, oracle11g First, you can select either desktop or server. The desktop class is relatively simple and requires no configuration. During installation, you are prompted to enter the

How to force oracle select and oracleselect In most cases, the built-in query optimization policy of the oracle database is still very successful, but occasionally, even if there is an index, full table scanning will be performed, you can refer to

Oracle Partition Outer Join thickening report, oracleouter Partition outer join converts sparse data into dense data. For example: With t as (select deptno, job, sum (sal) sum_sal from emp group by deptno, job), tt as (select distinct job from t)

A set of basic JDBC (Oracle database with Eclipse) OperationsJDBC: JDBC (Java Data Base Connectivity, java database connection) is a Java API used to execute SQL statements. It can provide unified access to multiple relational databases, it consists

MongoDB conventional backup policyMongoDB backup is actually a basic operation. Someone has been asking about it recently. It seems that many people are not familiar with it yet. In order to avoid repeated explanations, We will summarize a blog for

ORACLE restricts some IP addresses and malicious operations on important tables1. Problem Description The default oracle account has no restriction on ip addresses. The hidden danger is that if I know the username and password of the oracle account,

Oracle tablespace operations-- View the tablespace SELECT tablespace_name, file_id, file_name, round (bytes/(1024*1024), 0) | 'M' total_spaceFROM dba_data_filesORDER BY tablespace_name; -- create tablespace testlogging datafile

Oracle SQL tracking Select * from v $ sqlarea t where t. SQL _text like '% _ 070%' order by t. LAST_ACTIVE_TIME descSELECT * FROM v $ session st where st. SQL _ID = 'gabatezqjx0vc 'select t. hash_value, t. address from v $ sqlarea t where t. SQL

How to force oracle select cablingIn most cases, the built-in query optimization policy of the oracle database is still very successful, but occasionally, even if there is an index, full table scanning will be performed, you can refer to the