I have been trying to create a simple loop of SELECT statements in MySQL to reduce code. I have started this using CONCAT() however this causes the procedure to stop/fail. For example (where k is a loop counter):
CONCAT('SELECT (Child_', k, ' INTO #Age_Child_', k, ' FROM lookup_childage WHERE ModYear = ModYear_var LIMIT 1)');
To diagnose the issue, I simply tried to place the SELECT statement (without concatenated loop variables) inside a string to then be executed. While I could get this to work for simple statements it would not work for the following:
SET #queryString = CONCAT('SELECT Child_1 INTO #Age_Child_1 FROM lookup_childage WHERE ModYear = ModYear_var LIMIT 1');
PREPARE stmt FROM #queryString;
EXECUTE stmt;
Does anyone know why the #queryString containing the CONCAT() statement will not be executed/cause the procedure to fail?
tl;dr The statement you're trying to write has the form SELECT(rest of statement) LIMIT 1. It should have the form SELECT rest of statement LIMIT 1.
It looks like you want to create variable column names, ummm, because your lookup_childage table is denormalized. I guess that table has these columns.
Child_1 INT
Child_2 INT
Child_3 INT
Child_4 INT
It looks like you hope to get a #queryString value containing this sort of thing:
SELECT Child_4 INTO #Age_Child_4 FROM lookup_childage WHERE ModYear = ModYear_var LIMIT 1
Only the 4s are variable.
So to get that string you want
SELECT CONCAT('SELECT Child_', k,
' INTO #Age_Child_', k,
' FROM lookup_childage WHERE ModYear = ModYear_var LIMIT 1'
)
INTO #queryString;
I'm trying to update a column (in this case, a date) that is present on most of the tables on my database. Sadly, my database has more than 100 tables already created and full of information. Is there any way to loop through them and just use:
UPDATE SET date = '2016-04-20' WHERE name = 'Example'
on the loop?
One painless option would be to create a query which generates the UPDATE statements you want to run on all the tables:
SELECT CONCAT('UPDATE ', a.table_name, ' SET date = "2016-04-20" WHERE name = "Example";')
FROM information_schema.tables a
WHERE a.table_schema = 'YourDBNameHere'
You can copy the output from this query, paste it in the query editor, and run it.
Update:
As #PaulSpiegel pointed out, the above solution might be inconvenient if one be using an editor such as HeidiSQL, because it would require manually copying each record in the result set. Employing a trick using GROUP_CONCAT() would give a single string containing every desired UPDATE query in it:
SELECT GROUP_CONCAT(t.query SEPARATOR '; ')
FROM
(
SELECT CONCAT('UPDATE ', a.table_name,
' SET date = "2016-04-20" WHERE name = "Example";') AS query,
'1' AS id
FROM information_schema.tables a
WHERE a.table_schema = 'YourDBNameHere'
) t
GROUP BY t.id
You can use SHOW TABLES command to list all tables in database. Next you can check if column presented in table with SHOW COLUMNS command. It can be used this way:
SHOW COLUMNS FROM `table_name` LIKE `column_name`
If this query returns result, then column exists and you can perform UPDATE query on it.
Update
You can check this procedure on sqlfiddle.
CREATE PROCEDURE UpdateTables (IN WhereColumn VARCHAR(10),
IN WhereValue VARCHAR(10),
IN UpdateColumn VARCHAR(10),
IN UpdateValue VARCHAR(10))
BEGIN
DECLARE Finished BOOL DEFAULT FALSE;
DECLARE TableName VARCHAR(10);
DECLARE TablesCursor CURSOR FOR
SELECT c1.TABLE_NAME
FROM INFORMATION_SCHEMA.COLUMNS c1
JOIN INFORMATION_SCHEMA.COLUMNS c2 ON (c1.TABLE_SCHEMA = c2.TABLE_SCHEMA AND c1.TABLE_NAME = c2.TABLE_NAME)
WHERE c1.TABLE_SCHEMA = DATABASE()
AND c1.COLUMN_NAME = WhereColumn
AND c2.COLUMN_NAME = UpdateColumn;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET Finished = TRUE;
OPEN TablesCursor;
MainLoop: LOOP
FETCH TablesCursor INTO TableName;
IF Finished THEN
LEAVE MainLoop;
END IF;
SET #queryText = CONCAT('UPDATE ', TableName, ' SET ', UpdateColumn, '=', QUOTE(UpdateValue), ' WHERE ', WhereColumn, '=', QUOTE(WhereValue));
PREPARE updateQuery FROM #queryText;
EXECUTE updateQuery;
DEALLOCATE PREPARE updateQuery;
END LOOP;
CLOSE TablesCursor;
END
This is just an example how to iterate through all tables in database and perform some action with them. Procedure can be changed according to your needs.
Assuming you are using MySQL, You can use Stored Procedure.
This post is a very helpful.
Mysql-loop-through-tables
I'm trying to write a prodecure that updates a value in a given column-name where the users id equals given user ID.
_strong_1 is a variable that contains the column name, i.e: 'category_1', for example.
SELECT COLUMN_NAME FROM information_schema.`COLUMNS` C
WHERE table_name = 'subscribers_preferences' AND COLUMN_NAME LIKE _strong_1 INTO #columns;
SET #table = 'subscribers_preferences';
SET #s = CONCAT('UPDATE ',#table,' SET ', #columns = 1);
PREPARE stmt FROM #s;
EXECUTE stmt;
There's an error within the 'SET #s =' statement. I can get it to work with a simple SELECT statement, but UPDATE is being tricky.
Thanks in advance.
You need to put = 1 in quotes.
SET #s = CONCAT('UPDATE ',#table,' SET ', #columns, ' = 1');
Otherwise, you're comparing #columns with 1, and concatenating either 1 or 0 (probably always 0, since I doubt you have a column named 1) to the SQL, which is creating invalid SQL.
Note that the above code will only update one column. If #columns is supposed to hold 3 columns, you need to use GROUP_CONCAT in your query that sets it.
SELECT GROUP_CONCAT(CONCAT(column_name, ' = 1')) AS #columns
FROM information_schema.columns
WHERE table_name = 'subscribers_preferences' and column_name LIKE _strong_1;
SET #table = 'subscribers_preferences';
SET #s = CONCAT('UPDATE ',#table,' SET ', #columns);
I suspect you also need to add a WHERE clause to this SQL so it just updates the row for the given ID. As currently written, it will update all rows.
The fact that you need to write the query like this suggests improper normallization of your data. Instead of having each preference option in a different column, they should be different rows of the table, with the key being something like (user_id, setting_name).
I have stored procedure in my database and i need to look up a table and cross reference an id, then using the returned row i need to insert information into another table, but i cant seem to use the infomation from the lookup into the insert. This is what i have..
BEGIN
#Routine body goes here...
SET #UID = uid;
SET #UIDTOFB = uid_to;
SET #SQLTEST = CONCAT('SELECT users.user_auto_id FROM users WHERE users.user_fb_uid= #UIDTOFB LIMIT 1');
PREPARE sqlcmd from #SQLTEST;
EXECUTE sqlcmd;
INSERT INTO challenges(challenge_from_uid, challenge_to_uid, challenge_dateadded) VALUES(#UID, #SQLTEST.users.user_auto_id, now());
SET #LASTID = LAST_INSERT_ID();
SELECT #LASTID as id;
END
any help would be much appreciated!
This won't insert the value of #UIDTOFB since you missed some '. It takes this whole statement as one string and therefore the statement fails.
SET #SQLTEST = CONCAT('SELECT users.user_auto_id FROM users WHERE users.user_fb_uid= #UIDTOFB LIMIT 1');
PREPARE sqlcmd from #SQLTEST;
EXECUTE sqlcmd;
Anyway I'd recommend you use parameters like this:
PREPARE sqlcmd from 'SELECT users.user_auto_id FROM users WHERE users.user_fb_uid= ? LIMIT 1';
EXECUTE sqlcmd USING #UIDTOFB;
You can read more about it here in the manual.
UPDATE: Now I get, what you want to do. Do it simply like this:
SELECT #anyVariable:=users.user_auto_id FROM users WHERE users.user_fb_uid= #UIDTOFB LIMIT 1;
INSERT INTO challenges(challenge_from_uid, challenge_to_uid, challenge_dateadded) VALUES(#UID, #anyVariable, now());
How do you insert selected rows from table_source to table_target using SQL in MySQL where:
Both tables have the same schema
All columns should transfer except for the auto-increment id
Without explicitly writing all the column names, as that would be tedious
The trivial INSERT INTO table_target SELECT * FROM table_source fails on duplicate entries for primary key.
Either you list all of the fields you want in the insert...select, or you use something else externally to build the list for you.
SQL does not have something like SELECT * except somefield FROM, so you'll have to bite the bullet and write out the field names.
Column names have to be specified -
INSERT INTO table_target SELECT NULL, column_name1, column_name2, column_name3, ...
FROM table_source;
Just pass NULL as a value for the auto-increment id field.
Of course, primary key must be unique. It depends on what you want to achieve, but you could exclude rows with a primary key that already exists.
INSERT INTO table_target SELECT * FROM table_source
WHERE table_source.id NOT IN (SELECT id FROM table_target)
UPDATE: since you also need the extra rows, you should resolve the conflict first, does table_source have relationships? If not you could change those keys:
UPDATE table_source SET id = id + 1000
WHERE id IN (SELECT id FROM table_target)
Where 1000, is a constant, big enough so they go after the end of your table.
Tedious but safe and correct.
Writing INSERT statements without providing a list of columns leads to code that's hard to debug and, more importantly, very fragile code that will break if the definition of the table is changed.
If you absolutely can't write the column names out yourself then it's relatively easy to build a tool into your code that will create the comma-separated list for you.
This is my final solution to mass update with 'replace insert' command.
SET ##session.group_concat_max_len = ##global.max_allowed_packet;
SET #schema_db = 'db';
SET #tabl = 'table';
SET #cols = (SELECT CONCAT('`',GROUP_CONCAT(COLUMN_NAME SEPARATOR '`, `'), '`') FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = #schema_db AND TABLE_NAME = #tabl GROUP BY TABLE_NAME);
SET #Querystr = CONCAT('REPLACE INTO ',#schema_db,'.',#tabl,' SELECT ', #cols,' FROM import.tbl_', #tabl);
PREPARE stmt FROM #Querystr;
EXECUTE stmt;
I think you could use syntax like:
INSERT INTO table (a,b,c) VALUES (1,2,3)
ON DUPLICATE KEY UPDATE c=c+1;
REF: http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
Hope it helps
INSERT IGNORE just "bypass" the duplicate rows.
http://dev.mysql.com/doc/refman/5.5/en/insert.html
You can probably do it with prepared statements.
PREPARE table_target_insert FROM 'INSERT INTO table_target SELECT ? FROM table_source';
SET #cols:='';
SELECT #cols:=GROUP_CONCAT(IF(column_name = 'id','NULL',column_name) separator ",") FROM information_schema.columns WHERE table_name='table_source';
EXECUTE table_target_insert USING #cols;
It seems as if columns can not be given as a place holder in a MySQL Prepared Statement. I have compiled the following solution for testing:
SET #schema_db = 'DB';
SET #table = 'table';
SET #cols = (SELECT CONCAT(GROUP_CONCAT(COLUMN_NAME SEPARATOR ', '), "\n") FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = #schema_db AND TABLE_NAME = #table GROUP BY TABLE_NAME);
SET #Querystr = CONCAT('SELECT',' ', #cols,' ','FROM',' ',#schema_db,'.',#table,' ', 'Limit 5');
PREPARE stmt FROM #Querystr;
EXECUTE stmt;
You can use dynamic query:
DECLARE #Columns VARCHAR(MAX)=''
DECLARE #Query VARCHAR(MAX)=''
SELECT
#Columns = ISNULL(#Columns +',', '') + T.COLUMN_NAME
FROM
(
select name as COLUMN_NAME from sys.all_columns
where object_id = (select object_id from sys.tables where name = 'Source_Table')
and is_identity = 0
)T
set #Query = 'insert into Target_Table (' + SUBSTRING(#Columns,2 , 9999) + ') select ' + SUBSTRING(#Columns,2 , 9999) + ' from Source_Table';
PRINT #Query
EXEC(#Query)
The easiest way to do it is to use phpmyadmin to write the list of columns, then to change it as needed, in the example below I want to duplicate row with id=1078 and in this table I have id unique auto increment and alias unique.therefore I created my query as follow, with id & alias replaced by a desired value. and it worked like a charm.
INSERT INTO sy3_menuselect 1079, menutype, title, "alias", note, path, link, type, published, parent_id, level, component_id, checked_out, checked_out_time, browserNav, access, img, template_style_id, params, lft, rgt, home, language, client_id from sy3_menuwhere id=1078
Alternatively, to auto increment id, use the following Join statement:
INSERT INTO sy3_menuselect *
from (SELECT MAX(id+1 )from sy3_menu)a
join (select menutype, title, "alias", note, path, link, type, published, parent_id, level, component_id, checked_out, checked_out_time, browserNav, access, img, template_style_id, params, lft, rgt, home, language, client_idfrom sy3_menuwhere id=1079)b