PostgreSQL has excellent support for evaluating JSONPath expressions against JSON data.
For example, this query returns true because the value of the nested field is indeed "foo".
select '{"header": {"nested": "foo"}}'::jsonb #? '$.header ? (#.nested == "foo")'
Notably this query does not reference any schemas or tables. Ideally, I would like to use this functionality of PostgreSQL without creating or connecting to a full database instance. Is it possible to run PostgreSQL in such a way that it doesn't have schemas or tables, but is still able to evaluate "standalone" queries?
Some other context on the project, we need to evaluate JSONPath expressions against JSON data in both a Postgres database and Python application. Unfortunately, Python does not have any JSONPath libraries that support enough of the spec to be useful to us.
Ideally, I would like to use this functionality of PostgreSQL without creating or connecting to a full database instance.
Well, it is open source. You can always pull out the source code for this functionality you want and adapt it to compile by itself. But that seems like a large and annoying undertaking, and I probably wouldn't do it. And short of that, no.
Why do you need this? Are you worried about scalability or ease of installation or performance or what? If you are already using PostgreSQL anyway, firing up a dummy connection to just fire some queries at the JSONB engine doesn't seem too hard.
According to the MySQL documentation we can truncate the performance_schema with the help of the following call:
CALL sys.ps_truncate_all_tables(FALSE);
Internally this procedure is coded like follows. It actually executes TRUNCATE TABLE statements against a list of tables obtained with the masks '%summary%' and '%history%'.
The problem is that root user isn't able to perform the TRUNCATE TABLE statement on the performance_schema database in Google Cloud SQL due to superuser restrictions.
mysql> truncate table performance_schema.events_statements_summary_by_digest ;
ERROR 1227 (42000): Access denied; you need (at least one of)
the SUPER privilege(s) for this operation
I didn't find any Cloud SQL Admin API or other method to do this.
Any advice, how to reset the MySQL performance_schema in Google Cloud SQL without restarting DB instance.
UPD. I have found that it does not work for MySQL 5.7 but works well for MySQL 8.0 in Google Cloud SQL. So that if you can migrate your Google DB instance to MySQL 8.0 it would be workaround.
Currently there are no workarounds other than restarting the DB instances. And there is already a feature request raised for the same. You can +1 and CC yourself in the request to show interest in this being implemented and receive an email in case there are any updates.
In case you want to use performance_schema for database sql query analysis, as an alternative, you can use CloudSql Query Insights. Query insights helps you detect, diagnose, and prevent query performance problems for Cloud SQL databases. It supports intuitive monitoring and provides diagnostic information that helps you go beyond detection to identify the root cause of performance problems.
Or you can contact Google support, Product Team may offer up the stored procedure solution.
I'm trying to query on tables which are in oracle and postgres. here I have used two getconnection methods but while I'm trying to do some join operations it is giving me an error. This error is because of using or querying on a single resultset which has particular(either postgres or oracle) database connection. can we pass two database connections in a single getConnection() method?
note :- Written in scala
JDBC essentially works by sending a query to a database server and presenting the response of the server as a ResultSet to the developer. In other words it does not execute the query but hands it off the database which executes it. Hence JDBC can not magically execute a single query that combines tables from different database servers.
Some databases support linking multiple servers together. In that case you would have to configure the databases to know about each other, and then connect to one of them and send it a query that references the linked server in the correct format (which is different for every vendor). However not all vendors support linked servers, and even less support linking to servers of other vendors.
Another option is using something like spark which has its own query engine. Spark can use JDBC to download the data from both servers to your machine or spark cluster and then execute the query locally.
I have for years used MS Access and its query tool that is used for making queries. This tool is so good that I have never been forced to do very much SQL programming myself. The query tool has done all the work.
However, now I have started using Postgres and the Graphical Query Builder in pgAdmin. It seems that the Graphical Query Builder is rather primitive: It cannot be used if you need an aggregate function like SUM or COUNT.
Is this really correct?
Does anybody know a better graphical query builder for PostgreSQL?
Until now I have 'solved' the problem by linking MS Access to the Postgres database through ODBC and used MS Access' query tool to generate SQL commands which I then copy into pgAdmin's Graphical Query Builder - and edit the SQL commands until everything is correct.
SQL Maestro has a query designer, although it is PC only, AFAIK
http://www.sqlmaestro.com/products/postgresql/maestro/screenshots/getting_started/visual_query_builder/
EMS SQL Manager also has a query designer
http://www.sqlmanager.net/en/products/postgresql/manager/screenshots
Try SQLeo, its free and has a specific feature (autosavepoint) to prevent
ERROR: current transaction is aborted, commands ignored until end of transaction block.
Try a browser-based query builder for PostgreSQL called Skyvia. And you don’t have to worry about which operating system it works. It works where a browser exists. Simply make a connection to your PostgreSQL database and start building your queries. See a sample below.
Note that you can still switch between SQL code and query builder if you want to, just like in MS Access. Get the details here.
Is there any library where i can access mongodb by using sql like syntax.
Example
use db
select * from table1
insert into table1 values (a,b,c)
delete from table
select a,b,count(*) from table1 group by a,b
select a.field1,b.field2 from a,b where a.id=b.id
Thanks
Raman
The learning curve is small only if you are only doing extremely simple sql queries. If the extent of your SQL querying is "select * from X", then MongoDB looks like a brilliant idea to cut through all the too-complicated SQL. But if you need to perform left outer joins, test for null, check for ranges, subselects, grouping and summation, then you will soon end up with a round concave dent in your desk after being moved to Mongo. The sick punchline is that half the time, the thing you are trying to do can't be done in the Mongo interface. Mongo represents a bold new world where instead of databases doing things like aggregation and query optimization, it just stores data and all the magic is done by retrieving everything, slowly, storing it in app memory, and doing all that stuff in code instead.
YES!
A company called UnityJDBC makes a JDBC driver for mongodb. Unlike the mongo java driver, this JDBC driver allows you to run SQL queries against MongoDB and the driver is supported by any Java appliaction that uses JDBC.
to download this driver go to...
http://www.unityjdbc.com/mongojdbc/mongo_jdbc.php
Its free to download too!
hope this helps
MoSQL might satisfy your needs. It'll require you to run a new PostgreSQL instance but from there you can query your entire Mongo dataset with SQL.
"MoSQL imports the contents of your MongoDB database cluster into a PostgreSQL instance, using an oplog tailer to keep the SQL mirror live up-to-date. This lets you run production services against a MongoDB database, and then run offline analytics or reporting using the full power of SQL."
Have a look at this recent project: http://www.mongosql.com/. I've been looking at it over the last few weeks and it looks very promising.
For those of you who have questioned the usefulness of SQL against MongoDB, consider the large number of not-very-technical users in many organizations, like business analysts, who may know SQL, but don't want to make the leap to JavaScript and JSON. Tools like mongoSQL can help push the adoption of MongoDB in an organization.
There are a few solutions out there, but nearly all of them fail to truly represent the MongoDB data model in a way that the "relationally" minded ODBC/JDBC applications and users desire/require. A recent commercial product was released that addresses these challenges
ODBC:
http://www.progress.com/products/datadirect-connect/odbc-drivers/data-sources/mongodb
JDBC:
http://www.progress.com/products/datadirect-connect/jdbc-drivers/data-sources/mongodb
To address the need for ODBC/JDBC (SQL) access...While there are strong arguments for writing new applications using Mongo's clients, there is still a strong need in the marketplace for quality ODBC/JDBC and SQL based access to MongoDB. This need largely arises from all the reporting, analytic, and BI applications that rely on ODBC/JDBC connectivity and do not offer native integration with MongoDB.
Free NoSQL Viewer supports conversion of SQL queries to MongoDB shell syntax. Furthermore, in SQL Viewer you can even use SQL SELECT statements to query MongoDB collections data without knowing MongoDB query syntax. Check out NoSQL Viewer here www.spviewer.com/nosqlviewer.html
Mongodb and its current driver do not support direct SQL like syntax.
However, all operations are easily doable with the driver specific operations.
Here is a brief mapping of mongodb operations to corresponding SQL like query :
http://www.mongodb.org/display/DOCS/SQL+to+Mongo+Mapping+Chart
There are a couple projects underway to emulate a SQL interface for MongoDB. While they provide a familiar interface, in general they should be avoided. They operate on a fundamentally flawed premise in that they parse strings and translate them into method calls.
Once you work with MongoDB you will find the approach of using classes and methods a much more accessible interface as it works exactly like all other parts of your application. Yes there is a small learning curve as you first start, but for the most part, the interface in MongoDB works how you would expect it to.