Differences between mysql and oracle

Welcome to the Linux community forum and interact with 2 million technical staff. the difference between mysql and oracle databases in implementing auto-increment columns: mysql can implement auto-increment columns, As long as auto_increment is set during table creation, and oracle cannot set auto-increment columns during table creation, you must use the sequence to implement the auto-incrementing column function and establish the sequence

Welcome to the Linux community forum and interact with 2 million technical staff> enter 1. the difference between mysql and oracle databases in implementing auto-increment columns: mysql can implement auto-increment columns, As long as auto_increment is set during table creation, and oracle cannot set auto-increment columns during table creation, you must use the sequence to implement the auto-incrementing column function and establish the sequence

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1. Differences between mysql and oracle databases for auto-increment columns:

Mysql can implement auto-increment columns. You only need to set auto_increment when creating a table, but oracle cannot set auto-increment columns when creating a table,

You must use the sequence to implement the auto-incrementing column function. The statement for creating the sequence is as follows (assuming the sequence is named ts_sequence ):

Create sequence ts_sequence

Increment by 1 -- add several

Start with 1 -- count from 1

NOMAXVALUE -- do not set the maximum value

NOCYCLE -- always accumulate without repeating

CACHE 10;

After sequence is defined, you can use ts_sequence.nextval and ts_sequence.currval In the insert statement,

Ts_sequence.currval returns the current sequence value, but it must be used after the first ts_sequence.nextval initialization.

Ts_sequence.currval.

2. Differences between mysql and oracle Database indexes:

In the entire database, mysql indexes can have the same name, that is, mysql indexes are table-level, but Oracle indexes cannot have the same name, that is, Oracle indexes are database-level;

Mysql indexes start from 0 and oracle indexes start from 1.

The two indexes are the same:

Create index indexName on tableName (columnName );

Delete Index

Mysql:

Alter table tableName drop index indexName

Oracle:

Drop index indexName

Query the index of a table

Mysql:

Show index from tableName

Oracle:

Select index_name, table_name, column_name from user_ind_columns where table_name = 'tablename'