I want to add a prefix to tables and have recently written a PHP script to extract all tables in a string SQL query.
$sql = 'UPDATE festivals SET desc = "Starts from July"';
preg_match_all('/(from|into|update|table|join) (`?\w+`?)\s/i', $sql, $matches);
It works good but the only problem is that it extracts July because it does not distinguish between a SQL value and a real table name, so it assumes that July would be a table too.
Now I think the solution should be something to prevent extract what wrapped in a single or double quotation but don't know how to do that.
Your regex is better off this way:
"/((?:^select .+?(?:from|into))|^update|^table|join) (`?\w+`?)\s/I"
But I still agree with nvartolomei.
If you were more strict in your query-writing, you would wrap all your database, table and column names in backticks ` and they would be extremely easy to extract - just get the first match of a string between them: just make the backticks required instead of optional.
That said, I'm not entirely sure how your regex is matching from July since the July is not followed by whitespace...
Related
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
I'm new to php and sql , so could you please help me by telling me how to fix this sql error.
The sql is below.
INSERT INTO xml-group (id,groupid,name,descriptor,cust_id)
VALUES (1,1,'other contacts','other contacts',16)
The error is:
You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use
near '-group (id,groupid,name,descriptor,cust_id) VALUES
('0','0','mobiles','mobile',1' at line 1
Many thanks
The - isn't allowed in an unquoted table name. Use backticks to quote xml-group:
INSERT INTO `xml-group` (id,groupid,name,descriptor,cust_id)
VALUES (1,1,'other contacts','other contacts',16)
Btw, in a well designed database schema you might avoid such names and use _ instead.
use backticks arround table name it causes GROUP a special keyword of mysql
INSERT INTO `xml-group` (id,groupid,name,descriptor,cust_id)
VALUES (1,1,'other contacts','other contacts',16)
"-" Hyphen is not allowed in SQL syntax.
use backticks (`) symbol to escape it.
Also, if field ID is an auto-number field, primary index and "1" is already assigned, you'll get an error. (Same with any other fields that require unique values...)
Two options to fix it:
Replace xml-group with xml_group
Include backticks around it such as `xml-group`
Personally I would do both of those above options, but you can get away with just one.
You are best to enforce the use of back ticks for a few reasons. The primary reason I use back ticks myself is:
You do not have to worry about clashing with reserved or future key words.
Other reasons, but often dependant on personal preference and coding standards you have/can enforce on the whole code base are:
You can easily search the entire project for the use of that specific table. If for example you did SELECT user FROM users there is a good chance you have method names, variables, comments etc all containing the word "user" making it hard to find all the queries containing a reference to the user table amongst so many false positives. However, if you enforce the use of back ticks you just have to search for `users` to find all queries referencing it along with fields (as long as you haven't abstract the queries to the point where they are built up at runtime like: "SELECT `$field` FROM `$table`").
It can help with clarity and readability as it visually separates keywords from variable values like field names and table names even if everything is in lower case.
I have a short question about mysql query.
What is correct?
SELECT * FROM Persons WHERE Year='1965'
Or
SELECT * FROM `Persons` WHERE `Year` = '1965'
Is this a personal choice or is this something what is really wrong?
Quotes are needed if your identifiers (column, table names, operators, etc.) contain MySQL reserved words.
See here for the complete list of reserved words: http://dev.mysql.com/doc/refman/5.5/en/reserved-words.html
Both are correct, but the second one will ALWAYS be accepted, even when you use keywords or functions like while and NOW() that would normally be seen as operators.
What if you have a table named table, or a column named where. These are reserved keywords. If you used those in your queries without backticks, they'd produce an invalid query (Of course, using reserved keywords is bad practice).
SELECT something FROM table WHERE where = 1;
vs.
SELECT something FROM `table` WHERE `where` = 1;
Both methods are correct, the single quotation mark indicates starts and endings of a string.
Therefore if you for example use a column alias with a space like Birth year then you will need to use the single quotation mark like this;
... WHERE `Birth year` = `1965`
However it is not recommended only use more then one word in the aliases.
And as #Cody Caughlan said also when you use MySQL reserved words.
I am looking for a mysql query which will return me all the rows,
where a particular field is made up of characters from a given string.
e.g. I 've this string: $input = 'abcdef';
now, I am looking for mysql to result all those rows, where e.g. 'name' consists of letters from $input.
I hope I have expressed myself clearly.. :)
EDIT: Also, for the query you suggest, will it really improve performance, if we are just searching for strings made of letters a-z instead of some patterns, esp. when we are requesting data every 2 seconds.
The thing is that for now, my requirements are to only search among numeric, alpha or alphanumeric formats.. I will be using the exclusive patterns later on.
Regards
Nikhil Gupta
$query = "SELECT * FROM table WHERE `name` REGEXP '[" . mysql_real_escape_string($input) . "]'";
But this query is really weird and will be very slow (depends on how many rows you have).
SELECT `name` FROM `table` WHERE `name` REGEXP '^[abcdef]*$'
See MySQL: Regular expressions.
How can I match a word in a sentence from a column using regex? I tried:
"select * from table where column regex '/\b".$text."\b/i'"
but that didn't work.
Try this:
"SELECT * FROM table WHERE column REGEXP '[[:<:]]" . $text . "[[:>:]]'"
You should make sure that any characters that could be interpreted as special characters in $text are properly escaped. You should also ensure that you do not get an SQL injection.
MySQL is particularly bad about stuff like this. I'd recommend using MATCH AGAINST syntax http://dev.mysql.com/doc/refman/5.1/en/fulltext-search.html or using something like SOLR if you're going to be doing this in volume.
I think you want the LIKE clause!
SELECT * FROM table WHERE column LIKE '%value%'
Also please read UltimateBrent's answer as full text search is a very good point.