oracle query file

Oracle is a powerful relational database management system. Users can operate the database through query statements to achieve data retrieval, editing and other functions. In the Oracle database, in addition to querying table data, you can also query file data.

1. How to query files in Oracle

1. Use UTL_FILE package

Oracle database has a built-in UTL_FILE package, and users can use the functions provided by this package Read and write files directly. The UTL_FILE package includes the following procedures (PROCEDURE) and functions (FUNCTION):

• FCLOSE: Close an open file.
• FFLUSH: Flushes a cached file.
• FILEEXISTS: Determine whether the specified file exists.
• FOPEN: Open a file and return a file pointer.
• FREAD: Read data of the specified length from the file.
• FWRITE: Write data of specified length to the file.
• GET_LINE: Read a line of data from the file.
• ISOPEN: Determine whether a file has been opened.
• NEW_LINE: Insert a blank line into the file.
• PUT_LINE: Insert a line of data with specified content into the file.

For example, to query the contents of a text file in Oracle, you can use the following code:

DECLARE
fileHandler UTL_FILE.FILE_TYPE;
line VARCHAR2(200);
BEGIN
fileHandler := UTL_FILE.FOPEN('MY_DIR', 'myfile.txt', 'R');
LOOP

UTL_FILE.GET_LINE(fileHandler, line);
DBMS_OUTPUT.PUT_LINE(line);

END LOOP;
UTL_FILE.FCLOSE( fileHandler);
END;

The above code will open the file named "myfile.txt" and read the file contents line by line, and finally close the file.

2. Use external table query

Oracle database supports the concept of external table, that is, files are imported into the database as tables to form external tables. Users can query the same as ordinary tables. Query the external table.

First you need to create a directory in the Oracle database and authorize it to the specified user (MY_DIR is the folder name):

CREATE DIRECTORY MY_DIR AS 'C: ilefolder';
GRANT READ, WRITE ON DIRECTORY MY_DIR TO dbuser;

Next, you can use the following code to create an external table:

CREATE TABLE myfile
(
id NUMBER(10),
name VARCHAR2( 50)
)
ORGANIZATION EXTERNAL
(
TYPE ORACLE_LOADER
DEFAULT DIRECTORY MY_DIR
ACCESS PARAMETERS
(

records delimited by newline
fields terminated by ','
missing field values are null

)
LOCATION ('myfile .txt')
);

The above code imports the external file "myfile.txt" into the "myfile" table in the Oracle database, using commas as field separators and newline characters as record separators .

Then you can query like a normal table:

SELECT * FROM myfile;

2. Application scenarios of Oracle query files

1. Bill of materials import

In manufacturing and other fields, sometimes it is necessary to import the bill of materials. The bill of materials can be uploaded to the Oracle database in the form of a text file and the data can be read through query operations. It greatly facilitates business management.

2. Data Analysis

In the fields of data analysis, statistics and other fields, sometimes it is necessary to import a large amount of data into the Oracle database, and obtain valuable content by analyzing the data. Using the external table query function, files can be quickly imported into the Oracle database, reducing the tedious data filling work and improving efficiency.

3. Log file query

The server usually generates a large number of log files. These log files can be easily queried through the UTL_FILE package to quickly find server problems. , to ensure the normal operation of the server.

4. Data Backup

Sometimes it is necessary to back up the data in the Oracle database to a file. When an error occurs in the data, the backup file can be quickly imported through the external table query function. Oracle database to restore data.

In short, the function of Oracle query files greatly expands the usage scenarios of Oracle database, while also reducing the user's workload and improving efficiency. I hope this article can help readers have a deeper understanding of Oracle's method of querying files.

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