So I am new in SQL DEVELOPER tools and I have written a simple select statement like:
SELECT * FROM employee;
it worked fine but there was a yellow warning mark underneath SELECT and I clicked on that and my query changes into the following query:
SELECT "A1"."EMPLOYEE_ID" "EMPLOYEE_ID","A1"."FIRST_NAME" "FIRST_NAME","A1"."LAST_NAME" "LAST_NAME","A1"."SALARY" "SALARY", "A1"."DEPARTMENT_ID" "DEPARTMENT_ID","A1"."MANAGER_ID" "MANAGER_ID","A1"."HIRE_DATE" "HIRE_DATE"
FROM "INTRO_USER"."EMPLOYEE" "A1";
My Quest is what is the difference between these two queries? although their output is the same
The glob * has been expanded to all column of the table. The table name EMPLOYEE is aliased to A1 to make it shorter.
The feature you are seeing is called 'SQL Text Expansion,' and it's setup to allow you to see what your query would look like if you were working with one or more VIEWS.
For example, SELECT * FROM ALL_TABLES is quite complicated. This feature allows you to see what's actually involved when running that SQL.
https://www.thatjeffsmith.com/archive/2014/12/sql-developer-and-a-12c-magic-trick/
There is probably no change or expected delta in the performance or execution plan of the 2 versions of your query.
One of my columns is called from. I can't change the name because I didn't make it.
Am I allowed to do something like SELECT from FROM TableName or is there a special syntax to avoid the SQL Server being confused?
Wrap the column name in brackets like so, from becomes [from].
select [from] from table;
It is also possible to use the following (useful when querying multiple tables):
select table.[from] from table;
If it had been in PostgreSQL, use double quotes around the name, like:
select "from" from "table";
Note: Internally PostgreSQL automatically converts all unquoted commands and parameters to lower case. That have the effect that commands and identifiers aren't case sensitive. sEleCt * from tAblE; is interpreted as select * from table;. However, parameters inside double quotes are used as is, and therefore ARE case sensitive: select * from "table"; and select * from "Table"; gets the result from two different tables.
These are the two ways to do it:
Use back quote as here:
SELECT `from` FROM TableName
You can mention with table name as:
SELECT TableName.from FROM TableName
While you are doing it - alias it as something else (or better yet, use a view or an SP and deprecate the old direct access method).
SELECT [from] AS TransferFrom -- Or something else more suitable
FROM TableName
Your question seems to be well answered here, but I just want to add one more comment to this subject.
Those designing the database should be well aware of the reserved keywords and avoid using them. If you discover someone using it, inform them about it (in a polite way). The keyword here is reserved word.
More information:
"Reserved keywords should not be used
as object names. Databases upgraded
from earlier versions of SQL Server
may contain identifiers that include
words not reserved in the earlier
version, but that are reserved words
for the current version of SQL Server.
You can refer to the object by using
delimited identifiers until the name
can be changed."
http://msdn.microsoft.com/en-us/library/ms176027.aspx
and
"If your database does contain names
that match reserved keywords, you must
use delimited identifiers when you
refer to those objects. For more
information, see Identifiers (DMX)."
http://msdn.microsoft.com/en-us/library/ms132178.aspx
In Apache Drill, use backquotes:
select `from` from table;
If you ARE using SQL Server, you can just simply wrap the square brackets around the column or table name.
select [select]
from [table]
I have also faced this issue.
And the solution for this is to put [Column_Name] like this in the query.
string query= "Select [Name],[Email] from Person";
So it will work perfectly well.
Hi I work on Teradata systems that is completely ANSI compliant. Use double quotes " " to name such columns.
E.g. type is a SQL reserved keyword, and when used within quotes, type is treated as a user specified name.
See below code example:
CREATE TABLE alpha1
AS
(
SEL
product1
type_of_product AS "type"
FROM beta1
) WITH DATA
PRIMARY INDEX (product1)
--type is a SQL reserved keyword
TYPE
--see? now to retrieve the column you would use:
SEL "type" FROM alpha1
I ran in the same issue when trying to update a column which name was a keyword. The solution above didn't help me. I solved it out by simply specifying the name of the table like this:
UPDATE `survey`
SET survey.values='yes,no'
WHERE (question='Did you agree?')
The following will work perfectly:
SELECT DISTINCT table.from AS a FROM table
Some solid answers—but the most-upvoted one is parochial, only dealing with SQL Server. In summary:
If you have source control, the best solution is to stick to the rules, and avoid using reserved words. This list has been around for ages, and covers most of the peculiarities. One tip is that reserved words are rarely plural—so you're usually safe using plural names. Exceptions are DIAGNOSTICS, SCHEMAS, OCTETS, OFFSETS, OPTIONS, VALUES, PARAMETERS, PRIVILEGES and also verb-like words that also appear plural: OVERLAPS, READS, RETURNS, TRANSFORMS.
Many of us don't have the luxury of changing the field names. There, you'll need to know the details of the RDBM you're accessing:
For SQL Server use [square_braces] around the name. This works in an ODBC connection too.
For MySQL use `back_ticks`.
Postgres, Oracle and several other RDBMs will apparently allow "double_quotes" to be used.
Dotting the offending word onto the table name may also work.
You can put your column name in bracket like:
Select [from] from < ur_tablename>
Or
Put in a temprary table then use as you like.
Example:
Declare #temp_table table(temp_from varchar(max))
Insert into #temp_table
Select * from your_tablename
Here I just assume that your_tablename contains only one column (i.e. from).
In MySQL, alternatively to using back quotes (`), you can use the UI to alter column names. Right click the table > Alter table > Edit the column name that contains sql keyword > Commit.
select [from] from <table>
As a note, the above does not work in MySQL
Judging from the answers here and my own experience. The only acceptable answer, if you're planning on being portable is don't use SQL keywords for table, column, or other names.
All these answers work in the various databases but apparently a lot don't support the ANSI solution.
Simple solution
Lets say the column name is from ; So the column name in query can be referred by table alias
Select * from user u where u.from="US"
In Oracle SQL Developer, pl/sql you can do this with double quotes but if you use double quotes you must type the column names in upper case. For example, SELECT "FROM" FROM MY_TABLE
Situation is following:
I have identified sql injection attack vector, and have following information about target table:
It has six columns. (Identified using "order by").
I can see output of 3 of them (table is displayed). two seems kind of enum value (integer in database?), and one is a date. I have very strong suspicion that col #6 is date column.
I'm almost sure the database is oracle. (ROWNUM works and LIMIT gives error).
I don't have error messages (always generic text is returned - "something went wrong").
Frontend is PHP if that matters. But there might be middle layer between it and database (e.g. java service), so I'm not sure where the query is being constructed.
E.g. following search query works as expected:
test' AND ROWNUM <= 5 ORDER BY 6--
EDIT-FROM-HERE:
Ok after help from comments, following query works:
test' UNION ALL SELECT null,null,null,null,null,null FROM dual--
(I was missing FROM dual part. Thank you #kordirko very much!)
This query adds one empty record in the output table (it is visually visible), so I'm definitely on the right track!
Now following line also works:
test' UNION ALL SELECT null,null,null,n't',null,null FROM dual--
I correctly identified 4th column and now it displays uppercase(?) letter T where I expected it to appear. So far so good. But it gives error when I input any string longer than 1 char! So following gives an error:
test' UNION ALL SELECT null,null,null,n'test',null,null FROM dual--
I'm no expert in SQL injection, and especially ORACLE (though have experience with MsSql).
I think the problem is something unicode-ansi-whateverencoding-related. For other rows (selected by original query before my UNION ALL SELECT addition) the 4th column gives multi-character normal strings. But when I try to inject desired string, it only works if it's one character, and also misteriously displays it in uppercase. I think this must be some encoding problem. I just discovered I needed n prefix for unicode string after 1 hour of searching and struggling. Maybe some Oracle gurus can quickly spot what mistake do I have in my query?
I am using SQLManager Lite for firebird and it was impossible so far to write a query which would do an operation on char/varchar columns. Character set is win1252.
A query like
select * from Person where name = 'John'
won't return any results despite the fact that the record exists in the database. A similar query on a numerical column works just fine.
AM I am missing anything here?
Also, this query runs fine from my application. The only issue is that I would like to be able to run it within SQLManager Lite too. As a side note, values for char and varchar columns are not displayed properly within the same SQLManager Lite.
change to like
select * from Person where name like 'John'
I'm trying to browse an ms-access data base on a mac. Best results so far, I had with using OpenOffice on a Mac like described here.
Now I can see all the tables. But when I try to access the data with selects, I only see 3 lines of the result set and the contents of string columns is only shown with the first letter.
However, somehow I can access all the data:
select count(*) from SomeTable gives me correct row count.
select * from SomeTable where SomeStringCol='SomeWord' returns the
expected row(s)(so the select seems to use more than the first
letter... and select * from SomeTable where SomeStringCol='S'
returns empty result)
Any idea why it is like it is and how to access the full data? (It's not necessary to go with OpenOffice, that was just the best way up to now)
select * from SomeTable where SomeStringCol='S' only selects those rows where the only text in SomeStringCol is the letter 'S'. This is probably unlikely (but not impossible)
You would need to change the query to select * from SomeTable where left(SomeStringCol, 1) ='S' or select * from SomeTable where SomeStringCol like 'S*'
. when I try to access the data with selects, I only see 3 lines of the result set
As mentioned in the comments to the blog post cited in the question, the unlicensed version of that ODBC driver is crippled and will only return 3 rows.
I recently answered a similar question here regarding LibreOffice Base on Linux. The solution was to use the (free) UCanAccess JDBC driver to connect LibreOffice to the Access database. The actual steps would be slightly different for Mac OS X, but the basic approach would be the same.
I finally installed MDB Tool which opened the full DB and allowed me csv-exports.