I usually use SQLDeveloper to browse the database, but I couldn't make it work with HSQLDB and I don't know which tables are already created…
I guess it's a vendor-specific question and not plain SQL, but the point is: how can I see the tables so I can drop/alter them?
The ANSI SQL92 standard for querying database metadata is contained within the INFORMATION_SCHEMA data structures.
I have no idea whether your database supports this or not, but try the following:
SELECT *
FROM INFORMATION_SCHEMA.TABLES
On further research, it appears that HSQLDB does support INFORMATION_SCHEMA, but with slightly non-standard naming.
All of the tables have SYSTEM_* prepended to them, so the above example would read
SELECT *
FROM INFORMATION_SCHEMA.SYSTEM_TABLES
I have no means of testing this, and the answer was found on sourceforge.
Awesome, thanks! Been scouring the Web for that info.
This will fetch only your tables' field info:
SELECT TABLE_NAME, COLUMN_NAME, TYPE_NAME, COLUMN_SIZE, DECIMAL_DIGITS, IS_NULLABLE FROM INFORMATION_SCHEMA.SYSTEM_COLUMNS WHERE TABLE_NAME NOT LIKE 'SYSTEM_%'
You can retrieve indexes, primary key info, all kinds of stuff from INFORMATION_SCHEMA.SYSTEM_TABLES.
Gotta love oo documentation :p
If you're on the command line, you may want to try the Hsqldb SqlTool, documented in the SqlTool Manual (hsqldb.org).
Put your database connection information in "~/sqltool.rc" and choose any DBNAME you want, substitute correct username and password, if known.
urlid DBNAME
url jdbc:hsqldb:/path/to/hsql/database
username SA
password
Install tool with: apt-get install hsqldb-utils (on Ubuntu)
Connect with hsqldb-sqltool DBNAME # on Ubuntu
Hint for other systems: java -jar YourHsqlJar.jar DBNAME
Show tables with: \dt
Show columns with: \d TABLENAME
Standard queries like: SELECT * FROM …;
Edit (append) last command with: :a
Quit with: \q
View special commands with: \? OR :?
Good luck!
Use the \dt command when you hit the >sql prompt in the command line for HSQLDB.
Check out DBVisualiser and SQuirreL SQL Client. Both of these have support for HSQLDB, and a GUI for editing/modifying/viewing the tables.
You run querying using hsql database manager, are you?
If you use this, below may give some hints:
Select your connection:
type: HSQL DATABASE ENGINE SERVER
Driver: jdbc.hsqldb.jdbcDriver
URL: jdbc:hsqldb:hsql://localhost/
Then, you will browse the database.
Related
I am connecting to Hive via an ODBC driver from a .NET application. Is there a query to determine if a table already exists?
For example, in MSSQL you can query the INFORMATION_SCHEMA table and in Netezza you can query the _v_table table.
Any assistance would be appreciated.
Execute the following command : show tables in DB like 'TABLENAME'
If the table exists, its name will be returned, otherwise nothing will be returned.
This is done directly from hive. for more options see this.
DB is the database in which you want to see if the table exists.
TABLENAME is the table name you seek,
What actually happens is that Hive queries its metastore (depends on your configuration but it can be in a standard RDBMS like MySQL) so you can optionally connect directly to the same metastore and write your own query to see if the table exists.
There are two approaches by which you can check that:
1.) As #dimamah suggested, just to add one point here, for this approach you need to
1.1) start the **hiveserver** before running the query
1.2) you have to run two queries
1.2.1) USE <database_name>
1.2.2) SHOW TABLES LIKE 'table_name'
1.2.3) Then you check your result using Result set.
2.) Second approach is to use HiveMetastoreClient APIs, where you can directly use the APIs to check whether the table_name exist in a particular database or not.
For further help please go through this Hive 11
When programming on Hive by Spark SQL, you can use following method to check whether Hive table exists.
if (hiveContext.hql("SHOW TABLES LIKE '" + tableName + "'").count() == 1) {
println(tableName + " exists")
}
If someone is using shell script like me then my answer could be useful. Assume that your table is in the default namespace.
table=your_hive_table
validateTable=$(hive --database default -e "SHOW TABLES LIKE '$table'")
if [[ -z $validateTable ]]; then
echo "Error:: $table cannot be found"
exit 1
fi
If you're using SparkSQL you can do the following.
if "table_name" in sqlContext.tableNames("db_name"):
...do something
http://spark.apache.org/docs/2.1.0/api/python/pyspark.sql.html#pyspark.sql.SQLContext.tableNames
Code similar to below one can find in many of my Spark notebooks:
stg_table_exists = sqlCtx.sql("SHOW TABLES IN "+ stg_db)
.filter("tableName='%s'" % stg_tab_name) .collect()
(made two-liner for readability)
I wish Spark would have an API call to check the same.
If you're using a scala spark app and SparkSQL you can do the following
if spark.catalog.tableExists("tablename") {do something}
How can I tranfer data between different DB Servers, this is a daily job,
i.e:
Insert into ServerA..table1
select data from ServerB.table2.
(this is just an example, the real situation is we select data from many servers, and then do some join, then insert into the destination).
We can not use SSIS, we can not use linked server,
How can we do this?
btw, this is a daily job, and the data is huge.
A simple command line BCP script should work for you. For instance:
bcp AdventureWorks2012.Sales.Currency out Currency.dat -T -c -SServer1
bcp AdventureWorks2012.Sales.Currency in Currency.dat -T -c -SServer2
Here's more details
The Sync Framework might be worth a look : http://msdn.microsoft.com/en-us/sync/bb736753.aspx
Look at this question:
SQL backup version is incompatible with this server
The first options from my answer should work for your case
You can use C#.net SqlBulkCopy method.
My answer was converted into comment but I'm adding some more info.
I guess you are looking for this answer on SO:
What is the best way to auto-generate INSERT statements for a SQL Server table?
Once you have the code, just add USE your_databasename_where_to_copy_data at the begining, execute and voila
Edit:
As you want to do it on the fly, using code, try some of the solutions provided on this question on SO. Basically it is similar to your code proposal, with some few differences, as for example:
INSERT INTO bar..tblFoobar( *fieldlist* )
SELECT *fieldlist* FROM foo..tblFoobar
How do I query the database name in Oracle SQL Developer? I have tried the following and they all fail:
SELECT DB_NAME();
SELECT DATABASE();
Why do these basic MySQL queries fail in SQL Developer? Even this one fails too:
show tables;
EDIT: I can connect to the database and run queries such as:
select * from table_name_here;
EDIT 2: The database type is Oracle, this is why MySQL queries are failing. I thought it was related to the database client not the database itself. I was wrong. I'll leave the question as is for other as lost as I was.
Once I realized I was running an Oracle database, not MySQL, I found the answer
select * from v$database;
or
select ora_database_name from dual;
Try both. Credit and source goes to: http://www.perlmonks.org/?node_id=520376.
try this:
select * from global_name;
You can use the following command to know just the name of the database without the extra columns shown.
select name from v$database;
If you need any other information about the db then first know which are the columns names available using
describe v$database;
and select the columns that you want to see;
I know this is an old thread but you can also get some useful info from the V$INSTANCE view as well. the V$DATABASE displays info from the control file, the V$INSTANCE view displays state of the current instance.
Edit: Whoops, didn't check your question tags before answering.
Check that you can actually connect to DB (have the driver placed? tested the conn when creating it?).
If so, try runnung those queries with F5
To see database name,
startup;
then type
show parameter db_name;
DESCRIBE DATABASE NAME; you need to specify the name of the database and the results will include the data type of each attribute.
I have the following problem, I need to put in a script that is going to run before the new version is rolled the SQL code that enables the pgAgent in PostgreSQL. However, this code should be run on the maintenance database (postgres) and the database where we run the script file is another one.
I remember that in SQL Server there is a command "use " so you could do something like:
use foo
-- some code
use bar
-- more code
is there something similar in PostgreSQL?
You can put in your file something like:
\c first_db_name
select * from t; --- your sql
\c second_db_name
select * from t; --- your sql
...
Are you piping these commands through the psql command? If so, \c databasename is what you want.
psql documentation
You can't switch databases in Postgres in this way. You actually have to reconnect to the other database.
PostgreSQL doesn't have the USE command. You would most likely use psql with the --dbname option to accomplish this, --dbname takes the database name as a parameter. See this link for details on the other options you can pass in you will also want to check out the --file option as well. http://www.postgresql.org/docs/9.0/interactive/app-psql.html
well after looking on the web for some time I found this which was what I need it
http://www.postgresonline.com/journal/archives/44-Using-DbLink-to-access-other-PostgreSQL-Databases-and-Servers.html
I tried to execute the DESCRIBE command via a database link, but this was the return message:
DESCRIBE <table>#<database>;
ERROR:
------------------------------------
ERROR: object <table> does not exist
1 rows selected
A SELECT on this table works well.
Does Oracle permitts DESCRIBE via a database link?
I'm using the Oracle SQL Developer 1.5.1.
Edit:
Is there another option to describe a table?
Thanks in advance!
You could do something with the all_tab_columns table to get some table information.
select column_name, data_type from all_tab_columns where table_name = 'TABLE_NAME';
I think DESCRIBE is a SQL*Plus feature. See here.
The easiest way to get the description of a table on a remote server would be:
CREATE OR REPLACE VIEW TMP_VIEW AS SELECT * FROM TABLE_A#SERVER
/
DESCRIBE TMP_VIEW
/
If you do a select of the metadata from all_tab_columns for that table present on the DBLink, it'll provide the description of the table.
For Ex:
select * from all_tab_Columns#dblink where table_name='ASDF' and owner='XYZ';
You seem to be using PL/SQL Developer.
DESCRIBE is not an SQL command, it's a query tool alias that gets converted into a series of queries to the system tables.
PL/SQL Developer can not describe tables from remote databases, while native SQL*Plus can.
I can't check it right now, but maybe select * from v$tables#remotedb doesn't give similar information?
In PL/SQL Developer, you can right-click on the table name from the tables folder and click on describe...which gives the same result as the describe command in native SQL plus.
Using Oracle SQL Developer I was able to use DESCRIBE to show the definition of a remote table. However, I had to use the notation
describe schema.table#database