Multiple values in MySQL variable

The following works as expected when there is a single value stored in a variable.

SET @a := "20100630";
SELECT * FROM wordbase W开发者_如何学GoHERE verified = @a;

But it does not work when there are multiple values stored in a variable.

SET @a := "'20100630', '20100701' ";
SELECT * FROM wordbase WHERE verified in (@a);

Do I need to use prepared statements for this?

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There's good solution described here: https://stackoverflow.com/a/11957706/1523961

So you can use something like this:

SET @a := '20100630,20100701';
SELECT * FROM wordbase WHERE FIND_IN_SET(verified, @a);

Also, if you're selecting the ids for @a from another table, you can come up with the following:

SET @a := (SELECT GROUP_CONCAT(id) FROM someTable where yourBooleanExpressionHere);
SELECT * FROM wordbase WHERE FIND_IN_SET(verified, @a);

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You cannot (as far as I am aware) store multiple values in a MySQL user defined variable. What you have done is create a string which contains:

'20100630', '20100701'

That is not two separate values, but a single string value, just as this is a single string value:

SET @a := "It's a single string, and that's the problem";

You need to use two separate variables, or prepare a statement, like this:

SET @a := "20100630";
SET @b := "20100701";

SET @sql = CONCAT(
    'SELECT * FROM wordbase WHERE verified IN (',
    @a,
    ',',
    @b,
    ')'
);


SELECT @sql;
+--------------------------------------------------------------+
| @sql                                                         |
+--------------------------------------------------------------+
| SELECT * FROM wordbase WHERE verified IN (20100630,20100701) |
+--------------------------------------------------------------+

PREPARE stmt FROM @sql;
EXECUTE stmt;

But that's kinda messy. Why do you need to use variables?

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Using GROUP_CONCAT and GROUP BY one could pull all values ( i.e. an id ) into a variable like so:

SET @var := (SELECT GROUP_CONCAT(id) FROM `table` WHERE `verified` = @verified GROUP BY verified);

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Something like this should work. Is it ok to use prepared statements to create temporary tables like this?

SET @a := "'20100630', '20100701'";
SET @sql = CONCAT('create temporary table pn1 SELECT * FROM wordbase WHERE verified IN (', @a, ')');
PREPARE stmt FROM @sql;
EXECUTE stmt;

select * from pn1;

---

SELECT GROUP_CONCAT(field_table1 SEPARATOR ',') FROM table1 into @var;

then

SELECT * FROM table2 WHERE field_table2 in(@var);

works fine for me

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FIND_IN_SET(column to find in , string csv) is a very handy method in case you have the string list of CSV:

SET @a := "'20100630', '20100701' ";
SELECT * FROM wordbase WHERE FIND_IN_SET(verified, @a);

if your variable is also coming from query then use this to set @a

SET @a := (SELECT GROUP_CONCAT(`id`) FROM `table`);

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If you need to use your variable for a select or delete you can use select in the select:

delete from  MPCurrentPayEntitlementAccrual where CurrentPayEntitlementID in (  select CurrentPayEntitlementID from MPCurrentPayEntitlement where PayRunID=myPayRunId by PayRunID desc);

That worked perfectly for me