Empseq.currval from DUAL;It is important to note that:The first nextval returns the initial value, and the subsequent nextval automatically increases the increment by value that you define, and then returns the incremented value. Currval always returns the value of the current sequence, but the currval is not used until the first
Oracle's sequence implementation is very flexible, so it also brings about some usability issues. How to obtain the sequence value generated by the new inserted records is significantly different from other databases, this document introduces five methods for reading the sequence Value of the newly inserted record.
Database scripts used for testing:
SQL> create
deleting an oracle sequence is the drop SEQUENCE sequence name;Suppose there is a table test whose primary key is test_id1) set up the increment sequence seq_test:Create sequence Seq_testIncrement by 1Start with 1MinValue 1 NomaxvalueNocylce2) Create a trigger that uses an
In Oracle, sequence is the so-called serial number, which is automatically increased every time it is obtained. It is generally used in places where the sequence numbers need to be sorted.1. Create SequenceFirst, you must have the create sequence or create any sequence permission,Create
Label:Oracle's sequence implementation is very flexible, so it also brings some usability issues, how to get the new insert record generated by the sequence value and other databases have a large difference, this article detailed the country introduced 5 to read the new insert record sequence value method.Database Scripts for testing:sql> CREATE TABLE T1 2
Label: In Oracle in the sequence serial number is called, every time, it will take the initiative to increase itself, by the sequence number needed to sort the general use.1. Create SequenceYou must first create sequence or create any sequence permissions.CREATE SEQUENCE emp
: used cyclically, and then returned with a large maximum value. CACHE: Specify the cache value. If the CACHE value is specified, Oracle can place some sequence in the memory in advance, so that the access speed is faster. After the cache is obtained, oracle automatically retrieves another group to the cache. The cache may be skipped. For example, if the database suddenly fails to be shut down (shutdown abort), the
Tags: working with data arart databases oracletextrom In Oracle, sequence is the so-called serial number, which is automatically incremented each time it is taken, and is typically used where serial numbers need to be sorted. 1, createsequence you first have to have createsequence or createanysequence permissions, createsequenceemp_sequenceincrementby 1-- Add a few STARTWITH1 each time -- counting starting from 1 NOMAXVALUE -- do not set the maximum
program Location": 9th Chapter \ Createsequencetable.sql.(3) when inserting a new record, use the "tempsequence" sequence you just created to automatically generate the value of the "NO" data column. Execute the following SQL code in "Sqlplus Worksheet", as shown in Figure 9.52.―――――――――――――――――――――――――――――――――――――INSERT into SCOTT. Sequence_table (NO)VALUES (SCOTT. Tempsequence. Nextval);―――――――――――――――――
The generation of primary keys in the database is usually generated by sequence, and the sequence knowledge of PG is mainly listed as follows:How to find the name of the sequence: Open the current database with Pgadmin, find the relevant sequence under Schemas->sequences, and then Selectnextval (' im_indicator_results_
In general, the sequence in the actual development process is often used in an object, it is very convenient to generate a primary key, but sometimes we need to reset it to zero, usually in the way is deleted and recreated.
Here's another way to look at this:
sql> Create sequence Seq_1 increment by 1-start with 1 MaxValue 999999999;
The sequence has been creat
minimum valueCycle: Translated to Chinese is a circle meaning, here is actually refers to the loop, when the sequence reaches the maximum/minimum value, starting from the initial value to continue to generate. The default is Nocycle, and no loop generation is made.Cache: A pre-assigned sequence that is stored in the cache and can be used to quickly access the serial number. Default is NoCache, that is, no
Label:Sequence: is a database object provided by Oacle to produce a series of unique numbers. L automatically provide a unique value L Shared objects L mainly used to provide primary key value L Loading sequence values into memory improves access efficiency To create a sequence: 1, to have the right to create a sequence created
Sequence operations in Oracle and use the previous initialization of sequence 1 create sequence myseqstart with 1 increment by 1 nomaxvalueminvalue 1 II Initialize sequence select myseq. nextval from dual; it is worth noting that if you write select myseq directly first. cur
Auto-Define Sequence number: Used to do "Order No."There will always be such a demand, but you may not have encountered it. Let me give an example: if the order number is generated in the form "date + serial number"(Whether the demand is stupid or not), like this: 2015052200001234, how to deal with it?If there is a serial number, it is better to solve. Start with 00000001, go to 99999999, then reset to a sequence
missing values equals the number of cache.
NoCache : Do not specify cache count, default cache 20
Order: Specifies that the ordering condition guarantees that the sequence is generated in the sequence requested. This condition applies to the RAC environment.
Noorder : The sequence is not guaranteed to be generated in the order requested.
Example:
CREATE
used:-SELECT statements that do not contain subqueries, snapshot, and VIEW-The INSERT statement is in the subquery.-In the value of the NSERT statement-UPDATE in SET
See the following example:Insert into emp VALUES(Em1_q. nextval, 'Lewis ', 'cler', 7902, SYSDATE, 1200, NULL, 20 );
SELECT empseq. currval from dual;
Note that:-The first NEXTVAL returns the initial value. The subsequent
Tags: ar using SP data div on Art BS asIn Oracle, sequence is the so-called serial number, each time it takes its own initiative to add it, usually in order to be ordered by serial number place.1. Create SequenceYou first have to have create sequence or create any sequence permissions,CREATE SEQUENCE emp_sequenceINCREM
Label:In Oracle, sequence is the so-called serial number, each time it takes its own initiative to add, usually in order to be ordered by serial number place.1. Create SequenceYou first have to have create sequence or create any sequence permissions,CREATE SEQUENCE emp_sequenceINCREMENT by 1--add a few each timeStart w
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