In a procedure I want to select a value from a specific table in all databases. I developed a code and reached to this point:
BEGIN
DECLARE dynamic_query LONGTEXT;
SET SESSION group_concat_max_len = 100000000;
SET dynamic_query = (
SELECT
GROUP_CONCAT(
"SELECT option_name AS _key, option_value as _value from ",
TABLE_NAME,
" where option_name like '",
"something%'" SEPARATOR ' union ')
FROM
(
SELECT
CONCAT(`database_name`,'.',`table_prefix`,'options') as TABLE_NAME
FROM `tablename`
WHERE `database_name` <> '' AND `table_prefix` <> ''
) AS tmp
);
SELECT dynamic_query;
END
And I copy the output and execute it and it works fine. But when I add a prepare statement like below I get an error which is mentioned in this bug.
PREPARE result_query FROM dynamic_query;
EXECUTE result_query;
DEALLOCATE PREPARE result_query;
Is there any other way so I can get my desired output?
P.S.: I'm using SET SESSION group_concat_max_len = 100000000; to expand group_concat's limit but I prefer another way because the number of databases are growing.
Related
I need to call a mySQL function for all columns in a table.
I know how to do it for a particular column
Like this:
UPDATE `table_name` set `column_name` = function_name(`column_name`)
But i have no clue how to do it for all columns at once.
Thanks in advance.
Little clarification: I dont want to manually mention all columns, as i probably could have 200 columns table.
But i have no clue how to do it for all columns at once.
You just can't - there is no such shortcut in the update syntax.
You can do this with a single update statement, but you need to enumerate each and every column, like:
update table_name set
column_name1 = function_name(column_name1),
column_name2 = function_name(column_name2),
column_name3 = function_name(column_name3)
An alternative would be to use dynamic SQL to programatically generate the proper query string from catalog table information_schema.columns, and then execute it. This seems uterly complicated for what looks like a one-shot task... But here is sample code for that:
-- input variables
set #table_schema = 'myschema';
set #table_name = 'mytable';
set #function_name = 'myfunction';
-- in case "GROUP_CONCAT()" returns more than 1024 characters
set session group_concat_max_len = 100000;
-- build the "set" clause of the query string
select
#sql := group_concat(
'`', column_name, '` = ', #table_schema, '.', #function_name, '(`', column_name, '`)'
separator ', '
)
from information_schema.columns
where table_schema = #table_schema and table_name = #table_name;
-- entire query string
set #sql := concat('update ', #table_schema, '.', #table_name, ' set ', #sql);
-- debug
select #sql mysql;
-- execute for real
prepare stmt from #sql;
execute stmt;
deallocate prepare stmt;
How can I get data from chosen table of my database?
I'm going to work with database in c# application and I have the database includes that tables:
MyTable1;
MyTable2;
...
And I have tbl variable that is equal to tbl = "MyTable2";. I want to execute the code as following:select * from tbl
I try to execute this code:
SELECT *
FROM (
SELECT TABLE_NAME
FROM information_schema.tables
WHERE TABLE_NAME = 'MyTable1'
);
But the code returned error that Every derived table must have its own alias
I want to get all data from table whose name is equal to my variable (tbl) and its value can also be changed. How can I do it?
You might be able to do this using a prepared statement in MySQL:
SELECT TABLE_NAME
INTO #table
FROM information_schema.tables
WHERE TABLE_NAME = 'MyTable1';
SET #query = CONCAT('SELECT * FROM ', #table);
PREPARE stmt FROM #query;
EXECUTE stmt;
SELECT *
FROM (
SELECT TABLE_NAME
FROM information_schema.tables
WHERE TABLE_NAME = 'MyTable1'
) AS Blah
Try this:
DECLARE #SELECT nvarchar(500)
SET #SELECT = 'SELECT * FROM ' + #tbl
EXECUTE sp_executesql #SELECT
New to MySQL, need help in translating the next query to MySQL
If exists (select * from INFORMATION_SCHEMA.COLUMNS where table_name= 'MyTable' and column_name = 'MyColumn')
begin
update MyTable set MyColumn='' where Code=21
end;
Based on the comments posted on your question, here is a code snippet that should answer your need. It works by first checking if the column exists in INFORMATION_SCHEMA, and then dynamically building a SQL query that is prepared, then executed. It the column does not exists, a dummy query is executed instead of the UPDATE. I tested it in this db fiddlde.
SET #dbname = DATABASE();
SET #tablename = "my_table";
SET #columnname = "my_column";
-- check if the column exists
SELECT COUNT(*) INTO #cnt
FROM INFORMATION_SCHEMA.COLUMNS
WHERE
(table_name = #tablename)
AND (table_schema = #dbname)
AND (column_name = #columnname)
;
-- build a dynamic SQL statement
SET #preparedStatement = (SELECT IF(
#cnt > 0,
CONCAT("UPDATE ", #tablename, " SET ", #columnname, " = '' WHERE my_code = 21;"),
"SELECT 1"
));
-- run the statement
PREPARE updateIfExists FROM #preparedStatement;
EXECUTE updateIfExists;
DEALLOCATE PREPARE updateIfExists;
I'm looking for a way to easily check each table of a MySQL database and make sure that a certain field contains one value only. I have tables named Authors, Titles, Places, etc.
Each table contains a field called xuser and it needs to ask "does the field xuser contain the value xy in all records of all tables".
Can someone push me in the right direction how to do this with a SQL query if this is possible?
Thanks for reading, regards
Nico
I've created stored procedure which checks all table for provided db:
DELIMITER $$
DROP PROCEDURE IF EXISTS `UTL_CHECK_BACKUP_FOR_USER` $$
CREATE PROCEDURE `UTL_CHECK_BACKUP_FOR_USER`(
IN i_database_name VARCHAR(255),
IN i_user_column_name VARCHAR(255),
IN i_user_column_value VARCHAR(255),
OUT o_result TINYINT(1)
)
BEGIN
DECLARE v_table_name VARCHAR(255);
DECLARE v_last_row_fetched TINYINT(3) DEFAULT 0;
DECLARE tables_cursor CURSOR FOR
SELECT table_name
FROM information_schema.tables
WHERE table_schema = i_database_name
;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_last_row_fetched = 1;
SET v_last_row_fetched = 0;
OPEN tables_cursor;
SET #query =
CONCAT(
'SELECT SUM(IF(user_column=''',
i_user_column_value,
''', 1, -1)) = 1 INTO #o_result FROM ( SELECT ''test'' AS user_column FROM information_schema.tables WHERE 1<>1 '
)
;
table_loop: LOOP
FETCH tables_cursor INTO v_table_name;
IF (v_last_row_fetched = 1) THEN
LEAVE table_loop;
END IF;
SET #query =
CONCAT(
#query,
' UNION SELECT DISTINCT(',
i_user_column_name,
') AS user_column FROM ',
v_table_name
)
;
END LOOP table_loop;
CLOSE tables_cursor;
SET v_last_row_fetched=0;
SET #query =
CONCAT(
#query,
' ) all_xusers;'
)
;
PREPARE stmt FROM #query;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
SET o_result = COALESCE(#o_result, 0);
END $$
DELIMITER ;
Just deploy this stored procedure to database.
And then it could be executed in the following way:
-- db_name, user_column_name, user_column_value, result
call UTL_CHECK_BACKUP_FOR_USER('test', 'xuser', 'xxx', #result);
select #result;
To get the rows from all three tables where xuser has the same value in all three tables you could use:
SELECT *
FROM authors a
JOIN titles t
ON t.xuser = a.xuser
JOIN places p
ON p.xuser = t.xuser
If you want to look at a specific xuser value you could add the following WHERE clause:
WHERE a.xuser = 'xy'
The first thing comes to my mind:
select sum(if(xuser='xxx', 1, -1)) = 1
from (
select distinct(xuser) from authors
union
select distinct(xuser) from titles
union
select distinct(xuser) from places
) all_xusers;
This will return 1 (true) if all tables contains records belonging ONLY to 'xxx' user. Otherwise (if there is no 'xxx' records or there is some other user records) it will return 0 (false).
I've put together a simple stored procedure in which two parameters are passed through to make it more dynamic. I've done this with a prepared statement in the "First Two Digits and Count of Records" section.
What I'm not sure of is if I can make the SET vTotalFT section dynamic with a prepared statement as well.
At the moment I have to hard-code the table names and fields. I want my vTotalFT variable to be assigned based on a prepared dynamic SQL statement, but I'm not sure of the syntax. The idea is that when I call my procedure, I could tell it which table and which field to use for the analysis.
CREATE PROCEDURE `sp_benfords_ft_digits_analysis`(vTable varchar(255), vField varchar(255))
SQL SECURITY INVOKER
BEGIN
-- Variables
DECLARE vTotalFT int(11);
-- Removes existing table
DROP TABLE IF EXISTS analysis_benfords_ft_digits;
-- Builds base analysis table
CREATE TABLE analysis_benfords_ft_digits
(
ID int(11) NOT NULL AUTO_INCREMENT,
FT_Digits int(11),
Count_of_Records int(11),
Actual decimal(18,3),
Benfords decimal(18,3),
Difference Decimal(18,3),
AbsDiff decimal(18,3),
Zstat decimal(18,3),
PRIMARY KEY (ID),
KEY id_id (ID)
);
-- First Two Digits and Count of Records
SET #s = concat('INSERT INTO analysis_benfords_ft_digits
(FT_Digits,Count_of_Records)
select substring(cast(',vField,' as char(50)),1,2) as FT_Digits, count(*) as Count_of_Records
from ',vTable,'
where ',vField,' >= 10
group by 1');
prepare stmt from #s;
execute stmt;
deallocate prepare stmt;
SET vTotalFT = (select sum(Count_of_Records) from
(select substring(cast(Gross_Amount as char(50)),1,2) as FT_Digits, count(*) as Count_of_Records
from supplier_invoice_headers
where Gross_Amount >= 10
group by 1) a);
-- Actual
UPDATE analysis_benfords_ft_digits
SET Actual = Count_of_Records / vTotalFT;
-- Benfords
UPDATE analysis_benfords_ft_digits
SET Benfords = Log(1 + (1 / FT_Digits)) / Log(10);
-- Difference
UPDATE analysis_benfords_ft_digits
SET Difference = Actual - Benfords;
-- AbsDiff
UPDATE analysis_benfords_ft_digits
SET AbsDiff = abs(Difference);
-- ZStat
UPDATE analysis_benfords_ft_digits
SET ZStat = cast((ABS(Actual-Benfords)-IF((1/(2*vTotalFT))<ABS(Actual-Benfords),(1/(2*vTotalFT)),0))/(SQRT(Benfords*(1-Benfords)/vTotalFT)) as decimal(18,3));
First, to use dynamic table/column names, you'll need to use a string/Prepared Statement like your first query for #s. Next, to get the return-value from COUNT() inside of the query you'll need to use SELECT .. INTO #vTotalFT.
The following should be all you need:
SET #vTotalFTquery = CONCAT('(select sum(Count_of_Records) INTO #vTotalFT from
(select substring(cast(', vField, ' as char(50)),1,2) as FT_Digits, count(*) as Count_of_Records
from ', vTable, '
where ', vField, ' >= 10
group by 1) a);');
PREPARE stmt FROM #vTotalFTquery;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
Please note: the variable name has changed from vTotalFT to #vTotalFT. It doesn't seem to work without the #. And also, the variable #vTotalFT won't work when declared outside of/before the query, so if you encounter an error or empty results that could be a cause.
SELECT CONCAT (
'SELECT DATE(PunchDateTime) as day , '
,GROUP_CONCAT('GROUP_CONCAT(IF(PunchEvent=', QUOTE(PunchEvent), ',PunchDateTime,NULL))
AS `', REPLACE(PunchEvent, '`', '``'), '`')
,'
FROM tbl_punch
GROUP BY DATE(PunchDateTime)
ORDER BY PunchDateTime ASC
'
)
INTO #sql
FROM (
SELECT DISTINCT PunchEvent
FROM tbl_punch
) t;
PREPARE stmt
FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;