I have a database of entries consisting of a 'name', 'id' and a 'description', but currently the 'description' field is set to the file path of a .txt file that actually contains the description content. Each .txt file's name is each row's 'id', plus the .txt extension and they all reside in the same directory.
Can I load and replace each 'description' field with the content from the relevant text file (using MySQL)?
You can't write a MySQL query directly that will read the description values from your file system. That would require the MySQL server to be able to read raw text from files in your file system. You Can't Do That™.
You certainly can write a program in your favorite host language (php, java, PERL, you name it) to read the rows from your database, and update your description rows.
You could maybe contrive to issue a LOAD DATA INFILE command to read each text file. But the text files would have to be very carefully formatted to resemble CSV or TSV files.
Purely using mysql this would be a difficult, if not impossible exercise because mysql does not really offer any means to open files.
The only way to open an external text file from mysql is to use LOAD DATA INFILE command, which imports the text file into a mysql table. What you can do is to write a stored procedure in mysql that:
Create a temporary table with a description field large enough to accommodate all descriptions.
Reads all id and description field contents into a cursor from your base table.
Loop through the cursor and use load data infile to load the given text file's data into your temporary table. This is where things can go wrong. The account under which mysql daemon / service runs needs to have access to the directories and fiels where the description files are stored. You also need to be able to parametrise the load data infile command to read the full contents of the text file into a single field, so you need to set the field and line terminated by parameters to such values that cannot be found in any of the description files. But, even for this you need to use a native UDF (user defined function) that can execute command line programs because running load data infile directly from stored procedures is not allowed.
See Using LOAD DATA INFILE with Stored Procedure Workaround-MySQL for full description how to this.
Issue an update statement using the id from the cursor to update the description field in your base table from the temporary table.
Delete the record from your temp table.
Go to 3.
It may be a lot easier to achieve this from an external programming language, that has better file manipulation functions and can update each record in your base table accordingly.
Related
I know how to import a text file into MySQL database by using the command
LOAD DATA LOCAL INFILE '/home/admin/Desktop/data.txt' INTO TABLE data
The above command will write the records of the file "data.txt" into the MySQL database table. My question is that I want to erase the records form the .txt file once it is stored in the database.
For Example: If there are 10 records and at current point of time 4 of them have been written into the database table, I require that in the data.txt file these 4 records get erased simultaneously. (In a way the text file acts as a "Queue".) How can I accomplish this? Can a java code be written? Or a scripting language is to be used?
Automating this is not too difficult, but it is also not trivial. You'll need something (a program, a script, ...) that can
Read the records from the original file,
Check if they were inserted, and, if they were not, copy them in another file
Rename or delete the original file, and rename the new file to replace the original one.
There might be better ways of achieving what you want to do, but, that's not something I can comment on without knowing your goal.
I have a text file to be imported in a MySQL table. The columns of the files are comma delimited. I set up an appropriate table and I used the command:
load data LOCAL INFILE 'myfile.txt' into table mytable FIELDS TERMINATED BY ‘,’;
The problem is, there are several spaces in the text file, before and after the data on each column, and it seems that the spaces are all imported in the tables (and that is not what I want). Is there a way to load the file without the empty spaces (other than processing each row of the text file before importing in MySQL)?
As far as I understand, there's no way to do this during the actual load of the data file dynamically (I've looked, as well).
It seems the best way to handle this is to either use the SET clause with the TRIM
function
("SET column2 = TRIM(column2)")
or run an update on the string columns after loading, using the TRIM() function.
You can also create a stored procedure using prepared statements to run the TRIM function on all columns in a specified table, immediately after loading it.
You would essentially pass in the table name as a variable, and the sp would use the information_schema database to determine which columns to upload.
If you can use .NET, CSVReader is a great option(http://www.codeproject.com/KB/database/CsvReader.aspx). You can read data from a CSV and specify delimiter, trimming options, etc. In your case, you could choose to trim left and right spaces from each value. You can then either save the result to a new text file and import it into the database, or loop through the CsvReader object and insert each row into the database directly. The performance of CsvReader is impressive. Hope this helps.
As the title says: I've got a bunch of tab-separated text files containing data.
I know that if I use 'CREATE TABLE' statements to set up all the tables manually, I can then import them into the waiting tables, using 'load data' or 'mysqlimport'.
But is there any way in MySQL to create tables automatically based on the tab files? Seems like there ought to be. (I know that MySQL might have to guess the data type of each column, but you could specify that in the first row of the tab files.)
No, there isn't. You need to CREATE a TABLE first in any case.
Automatically creating tables and guessing field types is not part of the DBMS's job. That is a task best left to an external tool or application (That then creates the necessary CREATE statements).
If your willing to type the data types in the first row, why not type a proper CREATE TABLE statement.
Then you can export the excel data as a txt file and use
LOAD DATA INFILE 'path/file.txt' INTO TABLE your_table;
Is it possible to open and read from a text file in a MYSQL stored procedure? I have a text file with a list of about 50k telephone numbers, and want to write a stored procedure that will open the file, read the 50k lines and store it as rows in a table. I cannot load the file directly using LOAD IN FILE as the table has additional columns that I have to set.
Thanks!
In the end I used LOAD IN FILE. Apparently you can set which columns get populated by using the SET keyword:
LOAD DATA LOCAL INFILE '/temp/input_file.txt' IGNORE INTO TABLE TEST.TEST_INSERT (INSERT_FIELD) SET VERSION=1, LIST_ID=ID_GEN(), CREATE_DATE=NOW(), CREATE_BY='TESTUSER';
I'm using myisam_ftdump -c to dump the occurrences of words in my fulltext column. What's the simplest way to insert that information into a new MySQL table?
Thanks for any help, it's appreciated.
Dump the results > to a file and use a LOAD DATA INFILE query to import the contents back into your new table.
Note:
For security reasons, when reading text files located on the server, the files must either reside in the database directory or be readable by all. Also, to use LOAD DATA INFILE on server files, you must have the FILE privilege.