I have tried this query to pull up multiple tables and columns it works but comes back blank.
select * from onshore.contracting where code between 18789 and 18798;
select * from onshore.safety_incident where code between 18789 and 18798;
For your immediate problem, the following SQL will work if you really want all the data:
select * from onshore.contracting where code between 18789 and 18798;
select * from onshore.safety_incident where code between 18789 and 18798;
... and so on.
These tables probably have different columns so you need a separate select statement for each one.
If you are going to do more with SQL then it really would be worthwhile to learn it. There is a free resource here: https://www.w3schools.com/sql, my contribution is at http://www.thedatastudio.net and there are many others. It is a bit dangerous to use SQL without understanding it.
Related
So I want to get the tables used in the query_history table by using EXPLAIN on the query_text in the query_history. I know that I can give the SQL to EXPLAIN and it will give me the tables used but I need to do this over many different queries and return it all at once.
Basically I have 3 queries in the query_history table as follows:
select * from a.table1
select * from a.table2
select * from a.table3
And I need to do something like this:
SELECT "objects"
FROM TABLE(EXPLAIN_JSON(SYSTEM$EXPLAIN_PLAN_JSON(query_history.query_text)))
WHERE "operation"='TableScan';
This would return:
a.table1
a.table2
a.table3
I cannot do this in a programming language because it is going to be put into a BI tool that can only use SQL.
Can anyone tell me how to replace the name of all the table names in a the SELECT/FROM statements?. I'm looking of a way that works well across vanilla queries as well as more complex ones with sub-queries and joins.
I.e.
New table name: new_table
Original query: SELECT * from table;
Result query: SELECT * FROM new_table;
Thanks a lot,
j
If your queries are as simple as what you're proposing, you should be able start by parsing the query which will give you a SqlSelect object. From there you can use getFrom to check if it's the table you want to change and setFrom to change it.
If you want to handle more complex queries, you should be able to implement the SqlVisitor interface to find all occurrences of the table to replace.
I have some SQL that is broken into two SELECT statements. The first SELECT statement inserts results INTO a temp table. The second SELECT statement is a COALESCE that reads data from the temp table the first one inserted data into. I need to be able to run these together (one after the other) and unfortunately cannot put these into a Stored Procedure due to the old reporting tool my company uses. The reporting tool must read from a VIEW or a TABLE. I wanted to put these into a VIEW, but have researched that a view cannot have more than one SELECT. Any ideas and examples on how to accomplish this? My original post/solution showing the SQL is in this post.
The temp table select could be converted to be a CTE (With clause), and the 2nd part the select query of the view.
Alternatively you could just inline it with sub-selects, but depending on complexity that might make it harder to maintain.
CREATE VIEW yourView AS
WITH myFirstSelect(someFields) AS
(
SELECT somefields FROM sometable
)
SELECT * from myFirstSelect
Docs : https://learn.microsoft.com/en-us/sql/t-sql/queries/with-common-table-expression-transact-sql?view=sql-server-2017
I am referring to Jordan's answer regarding "dealing with evolving schemas "Dealing with evolving schemas.
As I share similar problem I have tried to query tables with different schema and got the following results:
Select a,b,c
FROM (Select 1 as a, 2 as b), --Test_a
(Select 1 as a, 2 as b, 3 as c), --Test_b
runs fine...
I have put Test_a and Test_b into physical tables (all fields are nullable) and tried:
Select a,b,c
FROM (Select a,b, from BI_WORKSPACE.Test_a),
(Select a,b,c from BI_WORKSPACE.Test_b)
It also runs fine
but when i tried
Select a,b,c
FROM BI_WORKSPACE.Test_a,
BI_WORKSPACE.Test_b
It failed...
Is there a bug, something i do wrong?
the last sample is the one i am after as it allows me to "evolve" my schema over time. i would like to avoid altering schema of all existing tables whenever i add a column to support a new business need.
Many thanks for your help.
The reason for asking:
We hold our data in "Daily tables" so when querying we pay only for the period we are interested in.
As BQ doesn’t support "Dynamic SQL", we have created an offline process that takes a query template and generates a query for desired period. Something like:
Input:
Select a,b,c FROM [<Source>]
Output:
Select a,b,c FROM [MYDATASET.TABLE20140201], [MYDATASET.TABLE20140202], [MYDATASET.TABLE20140203], [MYDATASET.TABLE20140204] , [MYDATASET.TABLE20140205] , [MYDATASET.TABLE20140206] , [MYDATASET.TABLE20140207]
Our process is unaware of the query logic. Sometimes we add fields to support evolving business needs.
Using dynamic sub selects will complicate staff a lot, and altering the schema for all hundreds of existing tables is expensive and prone to mistakes.
Any suggestions?
I don't think the last query should work. You're asking for columns a,b, and c from two tables, but one of those tables doesn't have a column with that name. That looks like a query error to me, since you are explicitly asking for a column that doesn't exist on the table.
There is a workaround -- to use a subselect -- which you noticed, if you know that a field may be missing from one schema. The other workaround, of course, is to update the schema.
This seems like it is working as intended. If you don't agree, can you let me know why?
It's possible to select from union of tables with different schemas.
Simple trick is to use subquery with asterisk as Jordan proposed. There's no need to alter schema.
In your case this will work (legacy SQL dialect)
SELECT a,b,c
FROM ( SELECT * FROM BI_WORKSPACE.Test_a ),
( SELECT * FROM BI_WORKSPACE.Test_b )
Ok, here is my dilemma I have a database set up with about 5 tables all with the exact same data structure. The data is separated in this manner for localization purposes and to split up a total of about 4.5 million records.
A majority of the time only one table is needed and all is well. However, sometimes data is needed from 2 or more of the tables and it needs to be sorted by a user defined column. This is where I am having problems.
data columns:
id, band_name, song_name, album_name, genre
MySQL statment:
SELECT * from us_music, de_music where `genre` = 'punk'
MySQL spits out this error:
#1052 - Column 'genre' in where clause is ambiguous
Obviously, I am doing this wrong. Anyone care to shed some light on this for me?
I think you're looking for the UNION clause, a la
(SELECT * from us_music where `genre` = 'punk')
UNION
(SELECT * from de_music where `genre` = 'punk')
It sounds like you'd be happer with a single table. The five having the same schema, and sometimes needing to be presented as if they came from one table point to putting it all in one table.
Add a new column which can be used to distinguish among the five languages (I'm assuming it's language that is different among the tables since you said it was for localization). Don't worry about having 4.5 million records. Any real database can handle that size no problem. Add the correct indexes, and you'll have no trouble dealing with them as a single table.
Any of the above answers are valid, or an alternative way is to expand the table name to include the database name as well - eg:
SELECT * from us_music, de_music where `us_music.genre` = 'punk' AND `de_music.genre` = 'punk'
The column is ambiguous because it appears in both tables you would need to specify the where (or sort) field fully such as us_music.genre or de_music.genre but you'd usually specify two tables if you were then going to join them together in some fashion. The structure your dealing with is occasionally referred to as a partitioned table although it's usually done to separate the dataset into distinct files as well rather than to just split the dataset arbitrarily. If you're in charge of the database structure and there's no good reason to partition the data then I'd build one big table with an extra "origin" field that contains a country code but you're probably doing it for legitimate performance reason.
Either use a union to join the tables you're interested in http://dev.mysql.com/doc/refman/5.0/en/union.html or by using the Merge database engine http://dev.mysql.com/doc/refman/5.1/en/merge-storage-engine.html.
Your original attempt to span both tables creates an implicit JOIN. This is frowned upon by most experienced SQL programmers because it separates the tables to be combined with the condition of how.
The UNION is a good solution for the tables as they are, but there should be no reason they can't be put into the one table with decent indexing. I've seen adding the correct index to a large table increase query speed by three orders of magnitude.
The union statement cause a deal time in huge data. It is good to perform the select in 2 steps:
select the id
then select the main table with it