Mysql use variable as column name. When using a value in SELECT, WHERE, etc.

Mysql use variable as column name Statement:. You could use if then else to have a different insert statement for each situation, I want to have a code where i would declare a column name as variable and then use this variable to retrieve desired column from a certain table. [GetLeaveDays] -- Add the parameters for the stored procedure here @LeaveType varchar,@AdminId int AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with This is done with a pivot table. But when I give variable - its giving out put of Column Name itself. Improve this answer. DU_02 however i want to optimize my code and not depends on my hands to do it, can anyone help me with this problem? Should be like this: CASE WHE Ask questions and share your thoughts on the future of Stack Overflow. Of course if anyone sees a better way to do the same thing I would be glad know it. 6 docs): As a general rule, other than in SET statements, you should never assign a value to a user variable and read the value within the same statement. What are other possible alternatives? My code is as follows: While MySQL uses backticks for quoting identifiers by default, ANSI-compliant SQL (and indeed MySQL in ANSI SQL mode, as noted here) uses double quotes for quoting identifiers. Name = Name; Even you can also add database prefix like. Viewed 2k times Part of PHP Collective You could use the name field from the sys. A better approach is to make a 2nd column called 'year' and calculate your year there. Right now my columns are labeled 60, 59, 58, 57, 56, 55etc then the values of the rows hold the over/under at that hour leading up to the match. "S" is the correct value (my code for serviceable) supplied from the post form. – No, this does not work in my MySQL 5. C#: string columnName = "xy"; string sql = "SELECT id AS " + columnName + " FROM table_name"; VB: Dim columnName As String = "xy" Dim sql As String = "SELECT id AS " & columnName & " FROM table_name" You can also do that in a stored procedure with MySql. Select Sql to mention column as variable. ALTER PROCEDURE [dbo]. 1. If you positively need a column name as function parameter name, one way to avoid naming collisions is to use an ALIAS inside the function. SELECT INTO Multiple Variable in MySQL My problem is, that the name of the column depends on another column's value. columns query as a basis to perform the update on. , instead of saying Table. SQL does not support a variable in that position -- only an identifier. You may also be interested in the corresponding reference answer here on SO: How to set value of composite variable field using dynamic SQL I have a table that has column names like 25, 50, 100, etc. Adding variable data to column in SQL Server 2008. For dynamic queries, you should generate the full SQL dynamically, and use sp_executesql to execute it. Select column name that has the maximum I would like to make an SQL query to my MySQL database that only queries for columns that I have selected from multi-valued variables. Concatenate fields in Mysql. customers. In general, you could use dynamic sql to use variable column names, see e. Quote the separate column names and use String#replace Can I name a column name in my mysql tables? Skip to main content. 4. MYSQL assign column name to variable? 0. A user variable name can contain other characters if you quote it as a string or identifier (for example, @'my-var', @"my-var", or @`my-var`). So if you are getting the values for table and column names from user input, make sure you validate them properly! Simply using mysql_real_escape_string() or mysqli_real_escape_string() will not work on table and column names, because they are not No, i want the year number (2021) as column name (replacing "fld_year"). Stored procedure with string parameters, The short answer is that you cannot use variables as database, table, or column names in MySQL. col_A , I need to say You need to use dynamic sql to use variables as column names, try: @dt nvarchar(255) = '[15-04-2017]' ,@fg nvarchar(255)= 'XC 1 IEC' DECLARE @sql nvarchar(200)= 'Select ' + @dt + ' as dt from It is posible to use a variable from a select statemens as a column name in the same statement. Variable as part of column name. @Table: the table name. One solution for improve security would be to make sure that the input col does exists in the target table, using MySQL This gives the system conniptions. The key is that you CAN use numbers for table names. crete table test (s1 int(1), s2 int(2)); insert into test values(10, 20); create I am trying to pass test1 column names to procedure, but no success mysql> call testselect('col1','col2'); +-----+-----+ | FST | SCND | +-----+-----+ | col1 | col2 | +-----+-----+ It just ERROR 1054 (42S22): Unknown column '_field_name' in 'NEW' Is there anyway for me to use a variable in NEW/OLD aliases in trigger? Any help or respond would be I want to use a registry as a column name but the registry is variable and I don't know when it changes. To understand why binding a table (or column) name doesn't work, you have to understand how the placeholders in prepared statements work: they are not simply substituted in as (suitably escaped) strings, and the resulting SQL executed. function with a variable in MySQL. See the curse and blessing of dynamic sql – Taryn. string concat in mysql. is not a valid column name in SQL. davmos. I want to use a variable as column name in my SQL query. Renaming I want to select values from the column names given as variables. That means the SQL Driver will try to escape that variable when interpolating it, including quoting, which is not what you want for things like column names, table names, etc. Years down the road, you (or anyone who maintains your code) will be thanking you What's part of the generated SQL, and what's evaluated in order to create that are you trying to coalesce the column name, i. Darren Need help updating a table with variable columns using dynamic SQL. SE. But what if column names are dynamically supplied to T-SQL code? Can we use variables instead of column names in our query? Yes we can. The issue is likely the use of %s for the column name. Use a dynamic query and a java. But they do allow the use of reserved keywords or embedded spaces as table and column names. use variable as a column name in sql. UPDATE customers SET customers. User variables are written as @var_name, where the variable name var_name consists of alphanumeric characters, . laravel how to access column with number name of a table? 0. At the moment I am trying to continue on from where artfulsoftware leaves off; right now I can query for results that give me my desired column names. I suspect that MySQL variables will be helpful, but I can't figure it out. crete table test (s1 int(1), s2 int(2)); insert into test values(10, 20); Column_name, Column_value. DECLARE @Column varchar(25) SET @Column = 'Name' -- This can be another column also SELECT @Column FROM MyTable This shows me 'Name' as many times as there are rows in my table. And any way, no, you cannot set column names as PreparedStatement values. How to use a variable as a column name for a SELECT statement. Select the columns based on the condition. Example: Config (field) = 'Medicine' FieldContent (another field) = Fleet_No is a column name and DK07 CKA its value (these are vehicles). If I wrap the column name with [ ]: SELECT 'value' AS You can pass the column name but you cannot use it in a sql statemnt like . But apparently the following is not . If you want to select more than one column: SELECT GROUP_CONCAT(COLUMN_NAME) FROM information_schema. I have a MySQL database with a table that contains 4 columns, A, B, C, and D. If you want variable columns, use dynamic SQL: use the md part as a template and append as many LEFT JOIN clauses as you need. Select @Columnname From Table One could build a dynamic sql string and execute it like EXEC (@SQL) SQL Variables as Column names in Where Clause. And Ua are using deprecated mysql – underscore Commented Apr 27, 2013 at 19:01 I would like to concatenate column names in a way that the first part of the column name is a string and the second part is a number which is the result of another query. Select Dynamic column names from concatenated strings. then you do want to use %s to prevent SQL injections and enable quoting, among other things. PHP Mysql - Use a variable as column name in Select statement. use column value as column name mysql. Union view - write a view unioning multiple queries but add column to But, please be aware of the following (from the MySQL 5. The only problem I I have made a dashboard variable that contains all the column names. Query 1 would pull back your data, Query 2 would pull back the column names and in code when you build what ever structure you use to display you set the headers from the second query. For example, SELECT DISTINCT IFNULL(@var:=Name,'unknown') FROM Customers ORDER BY <some non-indexed expression> LIMIT 10 appears to evaluate the variable assignments before the order-by is done, so that the returned value of @var might not even is there a way to pass the column name as variable? c#; linq; entity-framework; Share. As a general rule (and therefore probably subject to exceptions), DBMS do not allow you to use placeholders (parameters) for structural elements of a query such as table names or column names; they only allow you to specify values such as column values. For example, Also change your original query to assign better names to the variables: SELECT item_name, YEAR( DATE ) as year , SUM( item_sold_qty ) as item_sold_qty FROM item JOIN sales ON item. Ask Question Asked 10 If I understand you correctly, you need to grab a column whose name is defined in a variable. This is a no-no with most database engines and will prevent any migration at a later time. Is it even possible to do what I want ? thanks. mysql CONCAT AS name? 0. You can only set column values as PreparedStatement values. Prepared statements - build the SQL statement then execute Case statement - in a procedure, check a column variable against possible values and run a different query for each. DU_01 WHEN DU_AUX = 2 THEN B. Need to assign a Column name through a variable SQL. To further address the asker's question, one possible use would be that you have a master table where each row corresponds to a new table you created (And can have other information about the table) while also having an auto increment integer column that gives the Using Macro VAriable as Column Name Static Text in PROC SQL Posted 10-28-2020 05:09 AM (8423 views) Hello Everyone, Im setting a macro variable CHARGE. select is not valid at this position for this server version expecting '(' with. Commented Jul 12, 2013 at 16:22. For me it is important that the column names are escaped, because they contain unusal characters like whitespaces and accented characters, and I can’t change that. Pass the Count(*) to variable via T-SQL. Dynamic Column name in MYSQL. DECLARE col_n VARCHAR (100) := 'X' ; Column name as variable in PL/SQL ORACLE. Modified 13 years, 5 months ago. When using a value in SELECT, WHERE, etc. In standard SQL, you cannot use variables to define column names in a CREATE TABLE statement. If you are writing queries that are going to be executed in a MySQL server that was not setup / is controlled by you, here is what you can do: Write all you SQL queries in ANSI SQL; Enclose them in the following MySQL specific queries: SET @OLD_SQL_MODE=@@SQL_MODE; SET SESSION SQL_MODE='ANSI'; -- ANSI SQL declare @sql nvarchar(max); -- generate the column names select @sql = coalesce(@sql + ',', '') + QuoteName defined by its structure. The problem is that mysql doesn't let you insert variables as anything other than values, but you can create a new string which contains a command with the variable's value as the column name and execute that. declare @Test As varchar(100) set @Test = 'Name' EXEC ('SELECT ' + @Test + ' FROM TestTable') The standard warning for these answers is be certain that you can control what gets put in the SQL statement or use restrictive rights (e. Commented Jan 13, 2011 at 12:48 @Quassnoi, I have Second, creating dynamic names for columns as you are asking is generally not a good idea and defeats some of the best advantages of a relational database. My goal is to try an pass a variable from an ASP page to a stored procedure, which is utilizing the variable as criteria for a column name in the where clause. String whereClause = c + " = " + i; // Form the dynamic Query StringBuffer query = new StringBuffer( "SELECT * FROM TABLE" ); // Add WHERE clause if any query. using variables in my mysql stored procedure. Then just use SELECT * FROM Customers to retrieve the data. Or reference function parameters by ordinal position : $1 If you use a column name in the select part then that value will be selected for every record. For MySQL use `back_ticks`. Use variable names in select clause, need them to act like column name - SQL Server. 8. MySQL - Can I use a variable in place of a column name in SELECT. Example: WITH Q1 AS ( SELECT LENGTH(name) AS name_length, id, name FROM any_table ) SELECT id, name, name_length FROM Q1 WHERE name_length > 0 I want to create a temporary table, in which the columns will be those which I provide as parameter, separated by a delimiter. When I first came across this problem, it took me hell lot of time to find a simple solution to it. . As for easy reading, many people use caps for SQL keywords, eg. Is there any way that I can use my HOURSBEFOREMATCH integer as a variable to use that as a variable as a column name to INSERT it in the correct place? Hope this makes sense. – Erwin Brandstetter. Using a variable ColumnName. COLUMNS @YehCheez: I've never had this problem myself, because I use SQL for what it is: a language to give me data. If you absolutely must perfom such manipulations within MySQL, building a prepared statement is the way to go—although rather than messing around with CASE, I'd This is not possible. x where x can have the value of any of the columns A or B or C or D. Improve this question. Dynamic conversion of string into column name. But I am finding it difficult. User-defined variables are session specific. Similarly, next time the column number and names could vary. One of the rare cases where ALIAS is actually useful. item_number GROUP BY YEAR( DATE ) , item_name ORDER BY item_name The above assumes your mysql result array looks something like this: You do need to keep in mind that all the variables you use can lead to SQL injection. Viewed 6k times Now the First_Name, and Last_Name variable holds the column name of the below Dataframe Emp, Need the dataframe as below: DF = Emp. Here is an example of a script used to compare data between the same tables of different databases: Static query: There isn't anything wrong if you keep using MYSQL, except maybe the visual fuziness of the queries. mysql stored procedure, use column name as an argument. Name = eval(my_variable) It seems that eval() allow me to get a db object named by the variable value rather than a plain string object. how to use variable name as table name in update statement. I don't know how to ask this question but I would like to know if is it possible to declare the column names I want to get from a select. You can use SHOW COLUMNS FROM Customers to get the name of the columns. SQL Server Query using a Dynamic Column Name. Now, interesting enough, both select @code:=2, 2*@code and select @code:=rand(), 2*@code; do work in the same installation (today). Skip to main content. sql. LINQ - Accessing a column with the column name as a string parameter. I've a problem here, I need to use the name of the columns depends on my working day, as: CASE WHEN DU_AUX = 1 THEN B. UPDATE yourdb. About; use variable as a column name in sql. But MySQL functions do not support dynamic SQL. Please refer attached Image for Code It is example how use dynamic sql and cursor: create table test ( t1 int not null, t2 varchar(10) not null ) declare @query varchar(1000) select @query = ' declare @column int declare query cursor for select t'+cast(1 as varchar(1))+' from test open query fetch next from query into @column while(@@FETCH_STATUS=0) begin select @column fetch next from PHP variable in SQL column name. Better yet, you should probably work with a normalized table design. – Quassnoi. Unfortunately I'm lost on how to actually use the results as column names in a SELECT statement. Technically this variable itself is also based on a query, into the INFORMATION_SCHEMA. It becomes very difficult to feed the output into tables or other systems. Join our first live community AMA this Wednesday, February 26th, at 3 PM ET. Pass variable value as Column name in SPARK Sql/Pyspark? Ask Question Asked 3 years, 6 months ago. I have a Microsoft SQL stored procedure whose column name I want to set via a variable that is passed into it: CREATE PROCEDURE [My_Procedure] @myDynamicColumn varchar(50) AS BEGIN SELECT 'value' AS @myDynamicColumn END This does not work ("Incorrect syntax"). "if the column name is null, use the column name col instead"? If so, you have to do that outside the dynamic SQL string, in the format Use variable as column name. id = sales. Grouping by id, you issue CASE statements for each value you want to capture in a column and use something like a MAX() aggregate to eliminate the nulls and collapse down to one row. If you'd like to continue in this direction, you need to sanitize the column names (to avoid SQL Injection) and concatenate/build the SQL string yourself. How to pass column name as parameter in select statement SQL Server. Ask Question Asked 10 years, 5 months ago. MySQL use column names from another table. Follow answered Oct 11, 2012 at 19:07. While a Pure SQL Method may be possible it will be dynamic SQL and code maintnence would be a nightmare. Hot Network Questions Why have prison islands become much rarer? I am wondering why I cannot use variable column name like that: declare @a as varchar; set @a='TEST' select @a from x; Thank you I have month names as column names such as jan, feb, march, etc. It is very straight forward to use direct column names in T-SQL statements. 2. Dynamic SQL Add New Column and Work with it. I am getting x from the join with another table. `COLUMNS` WHERE `TABLE_SCHEMA`='databasename' AND `TABLE_NAME`='tablename'; I tried to get values of column names using: I am trying to assign a last column value on a table to a variable and it worked if I try my simple sql statement below : > declare @location nvarchar(50); > select @location = location FROM dbo. SQL Server dynamically adding column names in the select query. The only way to use a user variable as part of SQL syntax is to use a prepared statement, so you can build a SQL statement as a string before it is parsed. the respective table should contain the same amount and header names of the columns. Concatenating columns with mysql. So, instead, you need to You already found my answer recommending the hstore operator #= on dba. Here's an example: mysql> select * from test1 What i am trying to do is to make a procedure that selects value from test1 and then use this value as column name to select it from test2: DELIMITER // CREATE PROCEDURE How can variables be used as column name? Navigate: Previous Message• Next Message. edit_myTable( IN key CHAR(16), IN col VARCHAR(100), new _value using a variable for column name creates a risk of SQL injection. Selecting I have a sql server stored procedure where I want the table column name to be stored as variable. Is there any appropriate way of doing this except using a I'm not sure it is applicable for your case but in some circumstances it can be used to query a value by the column name without dynamic SQL: create table t1 ( a int, b int, c int ); insert It would probably be better to just use fixed names for this table (e. The syntax for defining a column name requires a column name to be specified as an identifier, which is a fixed string literal that does not vary during execution. select(col('Name1'),col('Name2'),col('Address')) I was wondering if there is a way to select a column by using a SQL variable. Commented Nov 22, 2021 at 15:22. , _, and $. Follow How to write select query along with IF condition in place of column name in mysql query. Posted by: Maris Radu Date: March 27, 2009 04:35AM It is posible to use a variable from a select statemens as a column name in the same statement. productcategory order by ProductCategoryID desc; print @location. The specific location is not important (or public). Store IN parameter in variable of Stored procedure. Thanks alot guys! Simplest way to distinguished between your parameter and column (if both name is same) is to add table name in your column name. Stack Overflow. g. This works in an ODBC connection too. @Template: what we want to retrieve using as a convention {cn} for . 6 setup; the second column yields NULL on first invocation, and returns 2 times the previous result if run again, which might fool one into thinking it did work. Table is - ID, Name, Address. This sounds prime for a front end display solution. Instead, a DBMS asked to "prepare" a statement comes up with a complete query plan for how it would execute that query, including In certain cases, the values left in variables might NOT correspond to the last row returned. Sql Server makes a distinction between a string containing a column name, and the column name itself, so you'll either need to use dynamic sql, or a case statement to translate the string to the actual column name as illustrated below: Case Statement (I'd SQL injection attracts sould be with your codes when we use variable directly to the SQl. I saw security warnings about the use of eval() but I gess it's OK since the evaluated variable doesn't come from user input. append(" WHERE " + whereClause); // Create a SQL statement context to execute the Query Statement stmt = con. How to concatenate strings to variables in Snowflake SQL. Passing FieldName as Parameter in MySQL Stored Procedure. For SQL Server use [square_braces] around the name. Thank you! – Miquel Martorell. So, given the Is it possible to alias a column name and then use that in a CASE statement? For example, SELECT col1 as a, CASE WHEN a = 'test' THEN 'yes' END as value FROM table; I am trying to alias the column You can't use variables like you want to; basically, if you want a variable identifier (table name, column name or the-like), you need to use dynamic SQL. PHP mysql_query - update using all variables. If CHARGE was a defined table alias or table name, For static queries, like the one in your question, table names and column names need to be static. CODE. e. The only way this is possible is with "dynamic SQL", Unlike some other RDBMS MySQL doesn't have native support for pivoting operations of this sort by design (the developers feel it's more suited to the presentation, rather than database, layer of your application). The only thing that you can do is to concatenate the sql statement as string and execute it as a prepared statement. Use variable sql for column name. Problem: I can not use dynamic SQL as the SQL query that I have is inside of a user defined inline table function. read-only) to execute them, otherwise you could get something like @Schema: the name of the schema of the table that we want to query. `COLUMNS` C WHERE table_name = 'MyTb' AND COLUMN_NAME LIKE '%whatever%' INTO @COLUMNS; SET How do I concat a string and a variable to use it as a column name in an sql query? Based on what Lennart suggested I have this now SET STMT = 'SELECT APPROP' || I have a MySQL database with a table that contains 4 columns, A, B, C, and D. MySQL select query with variable column name. Using a variable as a column name in a stored procedure? Ask Question Asked 13 years, 5 months ago. I can get the column names of table using: SELECT * FROM `INFORMATION_SCHEMA`. For example, if the preceding query needed to be done against a You will have to look at using dynamic sql if you want to use variables as the column names. customers SET yourdb. Options: Reply I need some help with my SQL logic, and I've been working (and researching) this for 2 days now with zero success. You would have to create the sql string dynamically. in my table. SET @s=CONCAT('ALTER TABLE dates ADD COLUMN `',dateStart,'` VARCHAR(30)'); PREPARE stmt1 FROM @s; EXECUTE stmt1; DEALLOCATE Using a variable as a column name in a stored procedure? 0. 23. Use MySQL variable only for counting without returning to client in Note that parameter symbols can only be used for data values — if you want to use dynamically determined table or column names, you must insert them into the command string textually. year 5, year 4, year 3, etc) for most of the query processing (and now you probably don't need to do it all as dynamic SQL) and then just apply the actual year names at the point where you actually present the data to the users. This is however not allowed in stored functions or triggers. Follow edited Sep 12, 2013 at 11:35. MySQL - How to use a variable as column name. createStatement(); // Execute the formed You can use EXEC to execute a fabricated SQL string:. 9,577 4 Get column name from Linq to Sql Entity. Hot Network Questions Expand or evaluate \bool_if or \tl_if_empty Can I make a column name from the variable equipment_stat, "Can I make a column name from the 'equipment_stat' variable" There may be a simple pure SQL solution for this. You would need to use dynamic SQL: DELIMITER // CREATE PROCEDURE myDB. As such, queries that quote identifiers with backticks are less easily portable to Syntax, including column names and other identifiers, must be fixed at the time the statement is parsed. If I want to display information in a column header in my app or website, I don't change the query, but use the programming language at I want to use Variable column name in Select Statement. MYSQL: Dynamic columns in mysql --> first, last name to full name: 5. 0. col_A , I need to say Table. 3. Let's say I have a query like this: SELECT field_1, field_2, Skip to main content. Note : My data in column is INT but Column Heading is Varchar. About; Products I suggest it would be in your best interest to treat the column name the same as you would treat any variable names, and give it a descriptive name. Hot Network Questions This also doesn't seem to work if the column name you're selecting shares the name with another actual column on any of the tables (from tables or joined tables) – Brian Leishman. For example, if the column names are: id, name, address. Commented May 7, Using Variable for Column name. For me, the simplest way to use an ALIAS in the WHERE clause is to create a sub-query and select from it instead. Share. I need to access those fields dynamically i. SQL Server Pass column name as where clause parameter. declaring multiple columns in a count value. Modified 1 year, 11 months ago. Postgres, Oracle and several other RDBMs will apparently allow "double_quotes" to be used. SELECT id, /* if col1 matches the name string of this CASE, return col2, otherwise return NULL */ /* Then, the outer MAX() aggregate will eliminate all NULLs and concat variable as column name in mysql select statement. Viorel has showed you how to use dynamic SQL with output parameters. Eg. Modified 9 months ago. Dotting the offending word onto the table name may also work. sumrr lkddbc doqq afqv xrgwdog jszeiu uaae ibjx ueuk vapxiu msbb pktqsria kzqxa ldwae vhtu