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
Related
Inside my database I have some tables that use a column with a reserved word name for example user, I have created it using " as "USER" but when I want to get it I have realized that I have to put it in capital letters, I have already investigated and I obtained that when placing " oracle respects it as case sensitive, they somehow know how to avoid this and obtain my column without the need for it to be written as defined, that is, case insensitive.
I am working Oracle with Firedac, on the Firedac side, do you know if something can be done so that this can be solved by having to put the column name as it is?
No.
You chose to have a column that conflicts with a reserved word, so you had to quote it when you declared it. You also need to quote this identifier everytime you use it - and a quoted identifier is case-sensitive by design.
I would strongly suggest avoiding having column names that conflict with SQL reserved word (or keywords). There is no benefit, and many drawbacks. You could just rename that column to usr, username, userid, or else. Declare the new name as a unquoted identifier, and you will never need to worry about this all afterwards.
I want to create a database containing multiple tables using postgres 11 and i'm currently creating a table which contain brackets in the heading of the column (as shown as follows).
Table - supp_details
supp_id|supp_name | supp_weight(Kg)|
Can i add units to the heading and what is the proper way to do so with sql?
I'm a fresher to query writing, so please help me with this.
You could place the column name in quotes, e.g. use "supp_weight(Kg)", but it is best to avoid placing special characters or keywords as object names. Instead, I suggest using the following name:
supp_weight_kg
It is just a single string requiring no escaping, and makes it clear what the units are. A better option might be to just use supp_weight, and maybe just keep a note somewhere that the column uses kilograms as the unit by default.
You will need to use quoted identifiers but I strongly recommend not to do that:
create table supp_details
(
supp_id integer,
supp_name text,
"supp_weight(kg)" integer
);
Adding bracket symbols into your column names is possible but probably a bad idea. If you want to micromanage the name just for display purposes of the end result, you should probably do it in an alias, using the AS keyword.
SELECT supp_id, supp_name, supp_weight AS "supp_weight(Kg)" FROM ...
Or add the decorations on the client side before it displays the results.
I'm wondering if it's possible to have a fieldname with parenthesis () and be able to call it with a query. For example I have a field name called...
EnoughMoney(0)
Select EnoughMoney(0) from tbl1
When I select it in SSMS i get the following error....
'EnoughMoney' is not a recognized built-in function name.
The way you can escape names (of columns or of anything else) in SQL Server is by enclosing them in square brackets. Your query will work if you write it like
select [EnoughMoney(0)] from tbl1
As correctly stated by others, it's usually a good practice to avoid spaces and special characters in database objects' names, unless you are forced to, obviously.
Use Select [EnoughMoney(0)] from tbl1
I tried to create table named 15909434_user with syntax like below:
CREATE TABLE 15909434_user ( ... )
It would produced error of course. Then, after I tried to have a bit research with google, I found a good article here that describe:
When you create an object in PostgreSQL, you give that object a name. Every table has a name, every column has a name, and so on. PostgreSQL uses a single data type to define all object names: the name type.
A value of type name is a string of 63 or fewer characters. A name must start with a letter or an underscore; the rest of the string can contain letters, digits, and underscores.
...
If you find that you need to create an object that does not meet these rules, you can enclose the name in double quotes. Wrapping a name in quotes creates a quoted identifier. For example, you could create a table whose name is "3.14159"—the double quotes are required, but are not actually a part of the name (that is, they are not stored and do not count against the 63-character limit). ...
Okay, now I know how to solve this by use this syntax (putting double quote on table name):
CREATE TABLE "15909434_user" ( ... )
You can create table or column name such as "15909434_user" and also user_15909434, but cannot create table or column name begin with numeric without use of double quotes.
So then, I am curious about the reason behind that (except it is a convention). Why this convention applied? Is it to avoid something like syntax limitation or other reason?
Thanks in advance for your attention!
It comes from the original sql standards, which through several layers of indirection eventually get to an identifier start block, which is one of several things, but primarily it is "a simple latin letter". There are other things too that can be used, but if you want to see all the details, go to http://en.wikipedia.org/wiki/SQL-92 and follow the links to the actual standard ( page 85 )
Having non numeric identifier introducers makes writing a parser to decode sql for execution easier and quicker, but a quoted form is fine too.
Edit: Why is it easier for the parser?
The problem for a parser is more in the SELECT-list clause than the FROM clause. The select-list is the list of expressions that are selected from the tables, and this is very flexible, allowing simple column names and numeric expressions. Consider the following:
SELECT 2e2 + 3.4 FROM ...
If table names, and column names could start with numerics, is 2e2 a column name or a valid number (e format is typically permitted in numeric literals) and is 3.4 the table "3" and column "4" or is it the numeric value 3.4 ?
Having the rule that identifiers start with simple latin letters (and some other specific things) means that a parser that sees 2e2 can quickly discern this will be a numeric expression, same deal with 3.4
While it would be possible to devise a scheme to allow numeric leading characters, this might lead to even more obscure rules (opinion), so this rule is a nice solution. If you allowed digits first, then it would always need quoting, which is arguably not as 'clean'.
Disclaimer, I've simplified the above slightly, ignoring corelation names to keep it short. I'm not totally familiar with postgres, but have double checked the above answer against Oracle RDB documentation and sql spec
I'd imagine it's to do with the grammar.
SELECT 24*DAY_NUMBER as X from MY_TABLE
is fine, but ambiguous if 24 was allowed as a column name.
Adding quotes means you're explicitly referring to an identifier not a constant. So in order to use it, you'd always have to escape it anyway.
What is the difference between single quotes and double quotes in SQL?
Single quotes are used to indicate the beginning and end of a string in SQL. Double quotes generally aren't used in SQL, but that can vary from database to database.
Stick to using single quotes.
That's the primary use anyway. You can use single quotes for a column alias — where you want the column name you reference in your application code to be something other than what the column is actually called in the database. For example: PRODUCT.id would be more readable as product_id, so you use either of the following:
SELECT PRODUCT.id AS product_id
SELECT PRODUCT.id 'product_id'
Either works in Oracle, SQL Server, MySQL… but I know some have said that the TOAD IDE seems to give some grief when using the single quotes approach.
You do have to use single quotes when the column alias includes a space character, e.g., product id, but it's not recommended practice for a column alias to be more than one word.
A simple rule for us to remember what to use in which case:
[S]ingle quotes are for [S]trings Literals (date literals are also strings);
[D]ouble quotes are for [D]atabase Identifiers;
Examples:
INSERT INTO "USERS" ("LOGIN", "PASSWORD", "DT_BIRTH") VALUES ('EDUARDO', '12345678', '1980-09-06');
In MySQL and MariaDB, the ` (backtick) symbol is the same as the " symbol. And note that you can't use " for literal strings when your SQL_MODE has ANSI_QUOTES enabled.
Single quotes delimit a string constant or a date/time constant.
Double quotes delimit identifiers for e.g. table names or column names. This is generally only necessary when your identifier doesn't fit the rules for simple identifiers.
See also:
Do different databases use different name quote?
You can make MySQL use double-quotes per the ANSI standard:
SET GLOBAL SQL_MODE=ANSI_QUOTES
You can make Microsoft SQL Server use double-quotes per the ANSI standard:
SET QUOTED_IDENTIFIER ON
In ANSI SQL, double quotes quote object names (e.g. tables) which allows them to contain characters not otherwise permitted, or be the same as reserved words (Avoid this, really).
Single quotes are for strings.
However, MySQL is oblivious to the standard (unless its SQL_MODE is changed) and allows them to be used interchangably for strings.
Moreover, Sybase and Microsoft also use square brackets for identifier quoting.
So it's a bit vendor specific.
Other databases such as Postgres and IBM actually adhere to the ansi standard :)
I use this mnemonic:
Single quotes are for strings (one thing)
Double quotes are for tables names and column names (two things)
This is not 100% correct according to the specs, but this mnemonic helps me (human being).
Two Things To Remember :
Single Qutoes(') : String Or Text
select * from employees where room_name = 'RobinCapRed';
where RobinCapRed is a string or a text.
Double Quotes(") : Column Names or Table Names
select "first_name" from "employees";
where first_Name is a column name from employees table
The difference lies in their usage. The single quotes are mostly used to refer a string in WHERE, HAVING and also in some built-in SQL functions like CONCAT, STRPOS, POSITION etc.
When you want to use an alias that has space in between then you can use double quotes to refer to that alias.
For example
(select account_id,count(*) "count of" from orders group by 1)sub
Here is a subquery from an orders table having account_id as Foreign key that I am aggregating to know how many orders each account placed. Here I have given one column any random name as "count of" for sake of purpose.
Now let's write an outer query to display the rows where "count of" is greater than 20.
select "count of" from
(select account_id,count(*) "count of" from orders group by 1)sub where "count of" >20;
You can apply the same case to Common Table expressions also.