Shulou(Shulou.com)06/01 Report--

(01) what are the components of a complete PLSQL?

[declare] / begin/ [exception] / end;/

(02) what do pename emp.ename%type and emp_rec emp%rowtype mean?

The pename variable is of the same type as the ename field of the emp table

The emp_rec variable has the same structure type as the emp table, through the variable name. Field name to access

(03) what does select to_char (sysdate,'day') into pday from dual mean?

Get the current day of the week set to the variable pday

(04) what does exit when cemp%notfound mean?

Exit when the cemp cursor cannot find the real record

(05) under what circumstances should cursor be used?

When you need to iterate over multiple records in a table from top to bottom, you can use cursor technology

(06) what does NO_EMP_FOUND exception mean?

Define exception

(07) what are stored procedures and stored functions?

A program segment with business functions written in oracle syntax, which is stored in the oracle server for a long time.

For oracle clients or external applications to call and return the corresponding results

(08) where are stored procedures and stored functions suitable for use?

The process is suitable for applications with no return value or more than one return value.

It is suitable to use a function when there is only one return value.

(09) what do in and out mean? Which is the default?

In receives arguments

Out output return value

Default is in

(10) what actions are triggers aimed at insert/delete/update/select?

The trigger is for insert/delete/update

01) oracle10i,oracle11g,oracle12c, what do you mean by other iMagnum gregory c?

I (internet)

G (grid)

C (cloud)

02) what does sqlplus mean?

Is a client tool that comes with oracle11g to connect to the server through the client for SQL operations

03) what are the requirements for the installation path and hardware configuration of oracle?

Directories that cannot be used in Chinese or blank strings

Hardware configuration at least: single CPU, 1G memory, 5G hard disk

04) what is PLSQL?

Is a procedural query language, a supplement to SQL (not a replacement), and can only be used in oracle database servers

05) how to insert 'quotation marks into the table?

Insert into emp (ename) values ('')

06) what is the function of decode () function?

Is a special multi-conditional judgment function for oracle, similar to the case...end syntax in SQL99

07) the difference between union and union all?

Union all means that what is the same in both sets can be taken out.

Union means that one of the two sets is the same, and only one can be taken

08) what is the difference between delete and truncate and drop?

Delete is DML/ rollable / where/-capable relatively slow / fragmented / content-free / structure has

Truncate is DDL/ non-rollback / non-stripable where/ relative / content none / structure has

Drop is DDL/ non-rollback / non-stripable where/ relatively fast / content no / structure none / can take purge keyword / flashback! = rollback

09) Why can it be rolled back in oracle?

Not all operations can be rolled back, only DML operations

Because the data of the DML operation is temporarily stored in the instance pool, the DML operation will be placed in the rollback area.

So for DML operations, it can be rolled back.

10) what is the difference between function and procedure?

Function is suitable for situations where there is only one return value

The procedure is suitable for situations where there are no return values or 2 or more return values.

11) what is the function of the cache of the sequence?

The purpose of the sequence is to provide a unique value for the primary key, but not necessarily continuous

With the cache mechanism, the primary key can be obtained directly from memory, and the speed is improved. The default is 20 primary key values.

It can be shared by multiple tables

12) briefly describe the relationship between users, roles and permissions?

Usually the key to the above three is many-to-many

Many to many-> one to many

13) talk about where the view is used?

First, allow users of different roles to access only what the users of that role can access.

Second, it simplifies the writing of complex SQL, but can not improve the query efficiency.

14) talk about the occasion where the index is used?

You can create indexes on single or multiple fields in a table to improve efficiency when querying based on that field

15) talk about pessimistic locks and optimistic locks?

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