set formula= REPLACE(upper(formula),upper(C_PHD_TAG), tagval);
set #replacevalue=CONCAT('SELECT ',#formula);
PREPARE myquery FROM #replacevalue;
EXECUTE myquery;
formula is'448.1879+405.8730+431.2464+407.9746' how to calculate this equation?
One approach is to use the EXECUTE method for prepared statement:
set #formula = '448.1879+405.8730+431.2464+407.9746';
set #query = CONCAT('SELECT ',#formula);
PREPARE myquery FROM #query;
EXECUTE myquery;
To store the result in a variable:
set #formula = '448.1879+405.8730+431.2464+407.9746';
set #query = concat('SELECT ',#formula, ' into #result');
prepare myquery from #query;
execute myquery;
select #result;
In the above,
#formula - holds the original formula for which the value should be calculated
#query - SQL statement that will be evaluated and produce the result of the formula
#result - variable that will contain the result after execution
myquery - name of the prepared statement (created by PREPARE, executed by EXECUTE)
See the link for the MySQL Execute Documentation
Related
I want to create a SQL script for MySQL 5.7 that inserts data from a table of a database origin into a table of another target database.
I want to have this source-database defined by a variable.
USE my_target_db;
SET #origin_db='my_origin_db';
SET #origin_table = concat(#origin_db,'.','tablename');
INSERT INTO target_table SELECT * FROM #origin_table;
Variables are used in various example to define column names but I never seen a way to define a table with it.
Is anyone has a trick for this ?
Variables won't use in table name in MySQL. You only can use a prepared statement for dynamic build query. For example:
USE my_target_db;
SET #origin_db='my_origin_db';
SET #origin_table = CONCAT(#origin_db,'.','tablename');
SET #query = CONCAT('INSERT INTO target_table SELECT * FROM ', #origin_table);
PREPARE stmt FROM #query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
You can read more detail about it in official documentation
You can use Prepared Statement like this:
USE my_target_db;
SET #origin_db='my_origin_db';
SET #origin_table = concat(#origin_db,'.','tablename');
SET #qry1 = concat('INSERT INTO target_table SELECT * FROM ', #origin_table);
PREPARE stmt1 from #qry1;
EXECUTE stmt1;
DEALLOCATE PREPARE stmt1;
Myself trying to pass string variable to where condition in MySQL query as given in this stack overflow answer as given below.
select #start := ' and Id=21';
select * from myTable where 1=1 #start;
So how can I use string variable with where condition in MySQL queries. The variables are set dynamically and the query runs within procedure.
EDIT: I also tried
SET #start = ' Id=21 ';
select * from myTable where (select #start);
But no use.
No you cannot do that. The columns and the condition in the select clause needs to be fixed when you are preparing the select statement.
So you cannot make a dynamic where clause statement like the one you posted. In that example, the values in the column are dynamic not the column names.
The manual says:
A conditional object consists of one or more conditional fragments
that will all be joined by a specified conjunction. By default, that
conjunction is AND.
I believe what you are attempting is to create a Dynamic Query using EXEC command.
You can create a varchar variable with the SQL statement and then execute it with EXEC, here an example taken from
https://www.mssqltips.com/sqlservertip/1160/execute-dynamic-sql-commands-in-sql-server/
If you want to do something like
DECLARE #city varchar(75)
SET #city = 'London'
SELECT * FROM customers WHERE City = #city
This is the Dynamic Query creation.
DECLARE #sqlCommand varchar(1000)
DECLARE #columnList varchar(75)
DECLARE #city varchar(75)
SET #columnList = 'CustomerID, ContactName, City'
SET #city = '''London'''
SET #sqlCommand = 'SELECT ' + #columnList + ' FROM customers WHERE City = ' + #city
EXEC (#sqlCommand) --This does the magic
/*
just a heads up, the user impersonating the execution needs credentials for EXEC command.
*/
Store part of your query
SET #start = ' and Id=21';
Store your query concatenating its parts
SET #s = CONCAT('select * from myTable where 1=1 ', #start);
Prepare a statement for execution
PREPARE stmt FROM #s;
EXECUTE executes a prepared statement
EXECUTE stmt;
Release the prepared statement
DEALLOCATE PREPARE stmt;
All together:
SET #start = ' and Id=21';
SET #s = CONCAT('select * from myTable where 1=1 ', #start);
PREPARE stmt FROM #s;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
More Details on the MySQL manual: https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-prepared-statements.html
I have this below piece of code. I would like to populate the KPI_RESULTS table using computed data from variable data. The variable data receives different fomulas. eg( n1*n7)*100 depending on the definition of the KPI fomula by the engineer. n1 ----n! are column names.
Am however getting an error when I try to execute the below scripts.
enter code here
set #data = 'n2/n1';
set #s = Concat("select datetime , element NODE,",#data," RESULTS from loas");
PREPARE STMT FROM #s;
INSERT INTO KPI_results(date_time,node_name,results) values(execute STMT );
That's unfortunately not supported. You'll have to PREPARE the dynamically generated INSERT query you want to run instead:
mysql> set #formula='n2/n1'
mysql> set #sql = CONCAT('INSERT INTO KPI_results SELECT foo, bar, ', #formula, ' FROM t')
mysql> PREPARE stmt FROM #sql
mysql> EXECUTE stmt
I'm trying to pass a table name into my mysql stored procedure to use this sproc to select off of different tables but it's not working...
this is what I"m trying:
CREATE PROCEDURE `usp_SelectFromTables`(
IN TableName varchar(100)
)
BEGIN
SELECT * FROM #TableName;
END
I've also tried it w/o the # sign and that just tells me that TableName doesn't exist...which I know :)
SET #cname:='jello';
SET #vname:='dwb';
SET #sql_text = concat('select concept_id,concept_name,',#vname,' from enc2.concept a JOIN enc2.ratings b USING(concept_id) where concept_name like (''%',#cname,'%'') and 3 is not null order by 3 asc');
PREPARE stmt FROM #sql_text;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
An extra bit that caused me problems.
I wanted to set the table name and field dynamically in a query as #kyle asked, but I also wanted to store the result of that query into a variable #a within the query.
Instead of putting the variable #a into the concat literally, you need to include it as part of the string text.
delimiter //
CREATE PROCEDURE removeProcessed(table_name VARCHAR(255), keyField VARCHAR(255), maxId INT, num_rows INT)
BEGIN
SET #table_name = table_name;
SET #keyField = keyField;
SET #maxId = maxId;
SET #num_rows = num_rows;
SET #sql_text1 = concat('SELECT MIN(',#keyField,') INTO #a FROM ',#table_name);
PREPARE stmt1 FROM #sql_text1;
EXECUTE stmt1;
DEALLOCATE PREPARE stmt1;
loop_label: LOOP
SET #sql_text2 = concat('SELECT ',#keyField,' INTO #z FROM ',#table_name,' WHERE ',#keyField,' >= ',#a,' ORDER BY ',#keyField,' LIMIT ',#num_rows,',1');
PREPARE stmt2 FROM #sql_text2;
EXECUTE stmt2;
DEALLOCATE PREPARE stmt2;
...Additional looping code...
END LOOP;
END
//
delimiter ;
So in #sql_text1 assign the result of the query to #a within the string using:
') INTO #a FROM '
Then in #sql_text2 use #a as an actual variable:
,' WHERE ',#keyField,' >= ',#a,' ORDER BY '
It depends on the DBMS, but the notation usually requires Dynamic SQL, and runs into the problem that the return values from the function depend on the inputs when it is executed. This gives the system conniptions. 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.
Some DBMS do have stored procedure support that will allow you to build up an SQL string and then work with that, using 'prepare' or 'execute immediate' or similar operations. Note, however, that you are suddenly vulnerable to SQL injection attacks - someone who can execute your procedure is then able to control, in part, what SQL gets executed.
I have to convert a MSSQL stored proc that passes a varchar that is a query:
INSERT INTO Results
EXEC (#Expresion);
This isn't working. I'm pretty sure that EXEC and EXECUTE aren't MySQL commands, but CALL doesn't work either.
Does anyone know if it's even possible to have something like JavaScript's eval function for MySQL?
I think you're looking for something like this:
SET #queryString = (
SELECT CONCAT('INSERT INTO user_group (`group_id`,`user_id`) VALUES ', www.vals) as res FROM (
SELECT GROUP_CONCAT(qwe.asd SEPARATOR ',') as vals FROM (
SELECT CONCAT('(59,', user_id, ')') as asd FROM access WHERE residency = 9
) as qwe
) as www
);
PREPARE stmt FROM #queryString;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET #asd = NULL;
This is the SQL equivalent of eval(my_string);:
#Expression = 'SELECT "Hello, World!";';
PREPARE myquery FROM #Expression;
EXECUTE myquery;
Basically I combined the existing answers, neither tells you how to do eval exactly.
If you want to add parameters, you can use this:
#username = "test";
#password = "asdf";
#Expression = 'SELECT id FROM Users WHERE name = ? AND pass = ?;'
PREPARE myquery FROM #Expression;
EXECUTE myquery USING #username, #password;
And to answer the original question exactly:
#Expression = 'SELECT "Hello, World!";'
PREPARE myquery FROM #Expression;
INSERT INTO Results
EXECUTE myquery;
Note that the PREPARE ... FROM statement wants a session variable (prefixed with #). If you try to pass a normal variable, it will throw its hands up in the air and it just won't care.
EXECUTE is a valid command in MySQL. MySQL reference manual
The EXECUTE MySQL command can only be used for one prepared statement.
If case you want to execute multiple queries from the string, consider saving them into file and source it, e.g.
SET #query = 'SELECT 1; SELECT 2; SELECT 3;';
SELECT #query INTO OUTFILE '/tmp/temp.sql';
SOURCE /tmp/temp.sql;