I have a Jackcess table and everything is working just fine. BUT I can't find anything on how to change a column name in the Jackcess table.
The reason I want to change the column name is that I have a ResultSet which is converted to Microsoft Access using Jackcess. a column is named "RELATION" but when Jackcess converts it, the name is changed to "xRelation". it must be some kind of Blacklisted word...
I want to change the column name back to "RELATION" and changing "RELATION" itself to something else is not an option.
How can I do this ?
Jackcess cannot alter the structure of the table after it has been created. So, if you want that column to be named Relation instead of xRelation you will probably need to
explicitly create the table first (e.g., using TableBuilder) with Relation as the column name, and then
use ImportUtil.importResultSet to import into the table you created:
ImportUtil.importResultSet(rs, db, "ExistingTable", new SimpleImportFilter(), true);
That form of importResultSet will import into an existing table instead of creating a new one.
Related
Currently I'm trying to import an SQL-INSERT dump from a postgres database into my Derby development/testing database using the Eclipse's Data Tools SQL scratchpad. The export created a lot of data that looked like the following:
CREATE TABLE mytable ( testfield BLOB );
INSERT INTO mytable ( testfield ) VALUES ('\x0123456789ABCDEF');
Executing it in Eclispe's SQL Scratchpad results in (translated from german):
Columns of type 'BLOB' shall not contain values of type 'CHAR'.
The problem seems, that the PostgreSQL admin tool exported BLOB data in a format like '\x0123456789ABCDEF' which is not recognized by Derby (Embedded).
Changing this to X'0123456789ABCDEF' or simply '0123456789ABCDEF'did also not work.
The only thing that worked was CAST (X'123456789ABCDEF' AS BLOB), but I'm not yet sure, if this results in the correct binary data when read back in Java and if the X'0123456789ABCDEF'is 100% portable.
CAST (...whatever... AS BLOB) doesn't work in java DB / Apache DERBY!
One must use the built-in system procedure
SYSCS_UTIL.SYSCS_IMPORT_DATA_LOBS_FROM_EXTFILE. I do not think there is any other way. For instance:
CALL SYSCS_UTIL.SYSCS_IMPORT_DATA_LOBS_FROM_EXTFILE (
'MYSCHEMA', 'MYTABLE',
'MY_KEY, MY_VARCHAR, MY_INT, MY_BLOB_DATA',
'1,3,4,2',
'c:\tmp\import.txt', ',' , '"' , 'UTF-8',
0);
where the referenced "import.txt" file will be CSV like (as specified by the ',' and '"' arguments above) and contain as 2nd field (I scrambled the CSV field order versus DB column names order on purpose to illustrate) a file name that contains the binary data in proper for the BLOB's. For instance, "import.txt" is like:
"A001","c:\tmp\blobimport.dat.0.55/","TEST",123
where the supplied BLOB data file name bears the convention "filepath.offset.length/"
Actually, you can first export your table with
CALL SYSCS_UTIL.SYSCS_EXPORT_TABLE_LOBS_TO_EXTFILE(
'MYSCHEMA', 'MYTABLE', 'c:\tmp\export.txt', ',' ,'"',
'UTF-8', 'c:\tmp\blobexport.dat');
to generate sample files with the syntax to reuse on import.
I want to modify MySQL database Table column name according to the jTable header name by java code
To rename column name
alter table tablename change oldname newname newcolumndatatype ;
check it
You can write java code which connect to MySQL database and rename columns by using above suggestion
Check with java sample code
I am doing a Java program in which I am reading input from some files and if it contains any string that I have in my list I have to update the table with name and its count.
First i created a table as follows
create table mobile(name varchar2(20),count int,primary key(name));
for instance,if I read string like "Sony unviels its new phone", table must be updated with name as sony count as 1.
what my doubt is initially it is an empty table. Can we update it as I said.
Thanks in advance....
First table creation
CREATE TABLE mobile
(
t_name VARCHAR (20),
t_count NUMBER,
PRIMARY KEY (t_name)
);
And insert statement
INSERT INTO mobile
VALUES ('Sony', 1);
Single statement for insert and update
MERGE INTO mobile t
USING (SELECT *
FROM mobile
WHERE LOWER (t_name) = 'sony') s
ON (t.t_name = s.t_name)
WHEN MATCHED
THEN
UPDATE SET t.t_count = t_count+1
WHEN NOT MATCHED
THEN
INSERT (t_name, t_count)
VALUES ('sony', 1);
Either you prepopulate you table with your given word list so something like
CREATE TABLE mobile(
name varchar2(20),
count_column int,
primary key(name)
);
INSERT INTO mobile (name, count_column) VALUES
('Sony', 0);
or you are adding some magic to your Java code which is deciding whether to do an UPDATE or an INSERT.
As an simple would look like theoretical
UPDATE mobile SET count_column to count_column+1 where name = 'Sony';
this will fail if there is none entry given.
You will have to execute an UPSERT like query , since oracle doesn't have it, you have to do a workaround to resolve this. please check this .
I created a table (using NetBeans I went to Databases, into jdbc, into app and created a table). I am 80% sure this is a SQL table but I could be wrong.
I named one of my columns as secretQuestion but now I need to change it to securityQuestion.
I looked online and found the following:
ALTER table app.mytable CHANGE secretQuestion to securityQuestion;
ALTER table app.mytable RENAME secretQuestion to securityQuestion varchar (100);
neither CHANGE nor RENAME are recognized.
I am a slow-witted newbie so be very specific in your answer so that I can follow along!
I am using Derby!
See here.
RENAME COLUMN statement
Syntax
RENAME COLUMN table-Name.simple-Column-Name TO simple-Column-Name
Examples
To rename the manager column in table employee to supervisor, use the
following syntax:
RENAME COLUMN EMPLOYEE.MANAGER TO SUPERVISOR
i have one syntax please remove 'to' keyword. it worked for me. Be sure about the table name and old column name
ALTER TABLE tablename CHANGE name newname DATATYPE;
If I have a SQL table with columns:
NR_A, NR_B, NR_C, NR_D, R_A, R_B, R_C
and on runtime, I add columns following the column's sequence such that the next column above would be R_D followed by R_E.
My problem is I need to reset the values of columns that starts with R_ (labeled that way to indicate that it is resettable) back to 0 each time I re-run my script . NR_ columns btw are fixed, so it is simpler to just say something like:
UPDATE table set col = 0 where column name starts with 'NR_'
I know that is not a valid SQL but I think its the best way to state my problem.
Any thoughts?
EDIT: btw, I use postgres (if that would help) and java.
SQL doesn't support dynamically named columns or tables--your options are:
statically define column references
use dynamic SQL to generate & execute the query/queries
Java PreparedStatements do not insulate you from this--they have the same issue, just in Java.
Are you sure you have to add columns during normal operations? Dynamic datamodels are most of the time a realy bad idea. You will see locking and performance problems.
If you need a dynamic datamodel, take a look at key-value storage. PostgreSQL also has the extension hstore, check the contrib.
If you don't have many columns and you don't expect the schema to change, just list them explicitly.
UPDATE table SET NR_A=0;
UPDATE table SET NR_B=0;
UPDATE table SET NR_C=0;
UPDATE table SET NR_D=0;
Otherwise, a simple php script could dynamically build and execute your query:
<?php
$db = pg_connect("host=localhost port=5432 user=postgres password=mypass dbname=mydb");
if(!$db) die("Failed to connect");
$reset_cols = ["A","B","C","D"];
foreach ($col in $reset_cols) {
$sql = "UPDATE my_table SET NR_" . $col . "=0";
pg_query($db,$sql);
}
?>
You could also lookup table's columns in Postgresql by querying the information schema columns tables, but you'll likely need to write a plpgsql function to loop over the query results (one row per table column starting with "NR_").
if you rather using sql query script, you should try to get the all column based on given tablename.
maybe you could try this query to get all column based on given tablename to use in your query.
SELECT attname FROM
pg_attribute, pg_type
WHERE typname = 'tablename' --your table name
AND attrelid = typrelid
AND attname NOT IN ('cmin', 'cmax', 'ctid', 'oid', 'tableoid', 'xmin', 'xmax')
--note that this attname is sys column
the query would return all column with given tablename except system column