I have a table with over a hundred columns, but I only want to select the the columns named nvarchar1, nvarchar2, ... nvarchar64. All of these 64 columns are next to each other so I was thinking maybe there is a way to select using column indices, but I couldn't find a solution.
Note: I don't want to do the obvious solution,
SELECT nvarchar1,
nvarchar2,
...
nvarchar64
...
Make use of the result from this query:
select column_name + ','
from information_schema.columns
where table_name = 'your table name'
and column_name like 'nvarchar%'
Related
I wanted to know a Query where in which i want to locate a specific table that contains two or more columns:
I tried:
SELECT *
FROM DB
WHERE TableName = 'TableName'
AND ColumName in('column1' , 'column2')
But this query will look if any of those columns are there, but i want it to return only if all of them are a match.
I hope this questions makes sense.
This should work for you in MySQL:
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE COLUMN_NAME in ('column1','column2')
AND TABLE_SCHEMA='your_database'
GROUP BY table_name
HAVING COUNT(COLUMN_NAME) =2;
The operator IN is a concatenation of OR. However, there's no way to creare a short concatenation of AND as well.
See this question.
Hi i need to concat all rows from my table.
I have this query select * from table1; this table contains 400 fields
i cannot do this select column1 ||','||column2||','||.....from table1
can someone help e to fix it using select * from table1 to concatinate all rows.
And thank you.
In Oracle (and similar in other DBMS) you could use system tables.... and do this in two steps:
Assuming you want to combine all the columns into 1 column for X rows...
STEP 1:
SELECT LISTAGG(column_Name, '|| Chr(44)||') --this char(44) adds a comma
within group (order by column_ID) as Fields
--Order by column_Id ensures they are in the same order as defined in db.
FROM all_tab_Cols
WHERE table_name = 'YOURTABLE'
and owner = 'YOUROWNER'
--Perhaps exclude system columns
and Virtual_Column = 'NO'
STEP 2:
Copy the results into a new SQL statement and execute.
The would look something like Field1|| Chr(44)||Field2|| Chr(44)||Field3
SELECT <results>
FROM YOURTABLE;
which would result in a comma separated list of values in 1 column for all rows of YOURTABLE
If the length of all the columns (along with , space and ||) would exceed the 4000 characters allowed... we can use a clob data type instead through the use of XML objects...
* Replace step 1 with *
SELECT RTRIM(XMLAGG(XMLELEMENT(Column_ID,Column_Name,'|| Chr(44)||').extract('//text()') order by Column_ID).GetClobVal(),'|| Chr(44)||') fields
FROM all_tab_Cols
WHERE table_name = 'YOURTABLENAME'
and owner = 'YOUROWNER'
--Perhaps exclude system columns
and Virtual_Column = 'NO';
Syntax for the above attributed to This Oracle thread but updated for your needs.
I have an Oracle database with many tables that have identical structure (columns are all the same). The table names are similar also. The names of the tables are like table_1, table_2, table_3...
I know this isn't the most efficient design, but I don't have the option of changing this at this time.
In this case, is it possible to make a single sql query, to extract all rows with the same condition across multiple tables (hundreds of tables) without explicitly using the exact table name?
I realize I could use something like
select * from table_1 UNION select * from table_2 UNION select * from table_3...select * from table_1000
But is there a more elegant sql statement that can be run that extracts from all matching table names into one result without having to name each table explicitly.
Something like
select * from table_%
Is something like that possible? If not, what is the most efficient way to write this query?
You can use dbms_xmlgen to query tables using a pattern, which generates an XML document as a CLOB:
select dbms_xmlgen.getxml('select * from ' || table_name
|| ' where some_col like ''%Test%''') as xml_clob
from user_tables
where table_name like 'TABLE_%';
You said you wanted a condition, so I've included a dummy one, where some_col like '%Test%'.
You can then use XMLTable to extract the values back as relational data, converting the CLOB to XMLType on the way:
select x.*
from (
select xmltype(dbms_xmlgen.getxml('select * from ' || table_name
|| ' where some_col like ''%Test%''')) as xml
from user_tables
where table_name like 'TABLE_%'
) t
cross join xmltable('/ROWSET/ROW'
passing t.xml
columns id number path 'ID',
some_col varchar2(10) path 'SOME_COL'
) x;
SQL Fiddle demo which retrieves one matching row from each of two similar tables. Of course, this assumes your table names follow a useful pattern like table_%, but you suggest they do.
This is the only way I know to do something like this without resorting to PL/SQL (and having searched back a bit, was probably inspired by this answer to count multiple tables). Whether it's efficient (enough) is something you'd need to test with your data.
This is kind of messy and best performed in a middle-tier, but I suppose you could basically loop over the tables and use EXECUTE IMMEDIATE to do it.
Something like:
for t in (select table_name from all_tables where table_name like 'table_%') loop
execute immediate 'select blah from ' || t.table_name;
end loop;
You can write "select * from table_1 and table_2 and tabl_3;"
I want to find the tables that contain both of the two columns together in one table. I tried this:
SELECT COLUMN_NAME, TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE COLUMN_NAME in ('CurrencyName', 'CurrencyKey');
This query generates all the tables that has either one of the CurrencyName or CurrencyKey column.
But I want the table that has both of these columns together.
Please shoot some ideas.
Thanks!
You are close. You want to use group by and then validate that you have two matches using a having clause:
SELECT TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE COLUMN_NAME in ('CurrencyName', 'CurrencyKey')
GROUP BY TABLE_NAME
HAVING COUNT(*) = 2;
Note: To be sure you have the right table, you should use TABLE_SCHEMA as well in the query.
how to
select name,family from student where name="X"
without its column name.
for example :
select "column1","column2" from student where "column1"="x"
or for example
select "1","2" from student where "1"="x"
"1" is column1
"2" is column2
i dont want to say columns name. i want to say just its number or other....
idont tired from select *. but it just for that i dont know the columns name but i know where they are. my columns name are change every i want to read the file but its data are same, and the data are in the same columns in each file.
Although you can not use field positions specifiers in the SELECT statement, the SQL standard includes the INFORMATION_SCHEMA where the dictionary of your tables is defined. This includes the COLUMNS view where all the fields of all tables are defined. And in this view, there is a field called ORDINAL_POSITION which you can use to assist in this problem.
If you query
SELECT ORDINAL_POSITION, COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'TABLE'
ORDER BY ORDINAL_POSITION
then you can obtain the column names for the ordinal positions you want. From there you can prepare a SQL statement.
You could use temp table as:
DECLARE #TB TABLE(Column1 NVARCHAR(50),...)
INSERT #TB
SELECT * FROM student
Then use it:
SELECT Column1 FROM #TB WHERE Column1='aa'
If it's a string you can do this :
Select Column1 + '' From Table
If it's a number you can do this :
Select Column1 + 0 From Table
If it's a datetime you can do this :
Select dateadd(d, 0, Column1) From Table
And similarly for other data types..
No, you can not use the ordinal (numeric) position in the SELECT clause. Only in Order by you can.
however you can make your own column alias...
Select Column1 as [1] From Table
You can use alias:
SELECT name AS [1], family AS [2] FROM student WHERE name="X"
It's just not possible. Unfortunately, they didn't think about table-valued functions, for which information_schema is not available, so good luck with that.