Split strings using mysql - mysql

Question

I want to create a stored procedure which will do matching of two tables. My requirement is to match two tables based on the columns user passes as an input.
Syntax:
CREATE PROCEDURE reconcile.matchTables(
IN TAB1 VARCHAR(25),
IN TAB1 VARCHAR(25),
IN COLS1 VARCHAR(250) ,
IN COLS2 VARCHAR(250))
EX:
matchTables('table1', 'table2', 'col1#col2#col3#col4' , 'col2#col13#col1#col8')
Now the stored procedure should form the where clause like the following
table1.col1 = table2.col2
and table1.col2 = table2.col13
and table1.col3 = table2.col1
and table1.col4 = table2.col8

Answer 1

MySQL does not include a function to split a delimited string. However, it’s very easy to create your own function.
User define function:
CREATE [AGGREGATE] FUNCTION function_name
RETURNS {STRING|INTEGER|REAL|DECIMAL}
Function:
CREATE FUNCTION SPLIT_STR(
x VARCHAR(255),
delim VARCHAR(12),
pos INT
)
RETURNS VARCHAR(255)
RETURN REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos),
LENGTH(SUBSTRING_INDEX(x, delim, pos -1)) + 1),
delim, '');
Usage:
SELECT SPLIT_STR(string, delimiter, position)

Answer 2

Answer
Table 1
CREATE TABLE `Table1` (
`Col1` varchar(100) DEFAULT NULL,
`Col2` varchar(100) DEFAULT NULL,
`Col3` varchar(100) DEFAULT NULL,
`Col4` varchar(100) DEFAULT NULL,
`DummyColumn` varchar(45) DEFAULT NULL
)
Table 2
CREATE TABLE `Table2` (
`col2` varchar(100) DEFAULT NULL,
`col13` varchar(100) DEFAULT NULL,
`col1` varchar(100) DEFAULT NULL,
`col8` varchar(100) DEFAULT NULL
)
Stored Procedure
CREATE DEFINER=`Connect7827`#`%` PROCEDURE `reconcile.matchTables`(
IN TAB1 VARCHAR(25),
IN TAB2 VARCHAR(25),
IN COLS1 VARCHAR(250) ,
IN COLS2 VARCHAR(250))
StartfromHere: BEGIN
DECLARE NoOfColumnInTable1 INT unsigned DEFAULT 0;
DECLARE NoOfColumnInTable2 INT unsigned DEFAULT 0;
Declare Column1Count int default 1;
Declare Column2Count int default 1;
Declare vPickOneValue varchar(100);
Declare querystring varchar(8000);
Declare NoOFRowsInFinalResult int default 1;
Declare _Tab1 varchar(1000);
Declare _TAB2 varchar(1000);
Declare _COLS1 varchar(1000);
Declare _COLS2 varchar(1000);
-- Column Names for Table 1
DROP TEMPORARY TABLE IF EXISTS Table1_Columns;
CREATE TEMPORARY TABLE Table1_Columns(Column_Name varchar(100));
SET #buffer= CONCAT_WS('','insert into Table1_Columns(Column_Name)
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = ',"'",TAB1,"'");
-- Select #buffer;
PREPARE stmt FROM #buffer;
EXECUTE stmt;
-- Column Names for Table 2
DROP TEMPORARY TABLE IF EXISTS Table2_Columns;
CREATE TEMPORARY TABLE Table2_Columns(Column_Name varchar(100));
SET #buffer= CONCAT_WS('','insert into Table2_Columns(Column_Name)
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = ',"'",TAB2,"'");
-- Select #buffer;
PREPARE stmt FROM #buffer;
EXECUTE stmt;
Set NoOfColumnInTable1=(Select count(*) from Table1_Columns);
Set NoOfColumnInTable2=(Select count(*) from Table2_Columns);
-- Select NoOfColumnInTable1,NoOfColumnInTable2;
if (NoOfColumnInTable1=0) then
Select 'Table 1 not found in database'as'Result';
leave StartfromHere;
end if;
if (NoOfColumnInTable2=0) then
Select 'Table 2 not found in database' as'Result' ;
leave StartfromHere;
end if;
IF (NoOfColumnInTable1!=NoOfColumnInTable2) then
Select 'No of column to be joined must be equal.'as'Result';
leave StartfromHere;
end if;
DROP TEMPORARY TABLE IF EXISTS BasedOn_Col1_List;
CREATE TEMPORARY TABLE BasedOn_Col1_List(ID int NOT NULL AUTO_INCREMENT, Column_Name varchar(100), PRIMARY KEY (id));
while Column1Count< NoOfColumnInTable1+1 do
set #Query=CONCAT_WS('' ,"insert into BasedOn_Col1_List(Column_Name) Select SUBSTRING_Index('",COLS1,"','#',",Column1Count,");");
-- Select #Query as'Value';
PREPARE stmt1 FROM #Query;
EXECUTE stmt1;
SET Column1Count=Column1Count+1;
end while;
SET Column1Count=1;
WHILE Column1Count<=NoOfColumnInTable1 do
SET vPickOneValue=(Select Concat(Column_Name,"#") from BasedOn_Col1_List where ID=Column1Count);
update BasedOn_Col1_List set Column_Name=replace(Column_Name,vPickOneValue,"") where ID<>Column1Count;
-- Select vPickOneValue;
SET Column1Count=Column1Count+1 ;
end while;
-- Preapre Table from Column2 Parameter
DROP TEMPORARY TABLE IF EXISTS BasedOn_Col2_List;
CREATE TEMPORARY TABLE BasedOn_Col2_List(ID int NOT NULL AUTO_INCREMENT, Column_Name varchar(100), PRIMARY KEY (id));
while Column2Count< NoOfColumnInTable2+1 do
set #Query=CONCAT_WS('' ,"insert into BasedOn_Col2_List(Column_Name) Select SUBSTRING_Index('",COLS2,"','#',",Column2Count,");");
-- Select #Query as'Value';
PREPARE stmt2 FROM #Query;
EXECUTE stmt2;
SET Column2Count=Column2Count+1;
end while;
SET Column2Count=1;
WHILE Column2Count<=NoOfColumnInTable2 do
SET vPickOneValue=(Select Concat(Column_Name,"#") from BasedOn_Col2_List where ID=Column2Count);
update BasedOn_Col2_List set Column_Name=replace(Column_Name,vPickOneValue,"") where ID<>Column2Count;
-- Select vPickOneValue;
SET Column2Count=Column2Count+1 ;
end while;
DROP TEMPORARY TABLE IF EXISTS TableFromColumnList;
CREATE TEMPORARY TABLE TableFromColumnList
( ID int NOT NULL AUTO_INCREMENT,
Table1Name varchar(100),
Column_Name_Table1 varchar(100),
Table2Name varchar(1000),
Column_Name_Table2 varchar(100),
PRIMARY KEY (id)
);
Insert into TableFromColumnList(Column_Name_Table1,Column_Name_Table2,Table1Name,Table2Name)
select t1.Column_Name,t2.Column_Name,TAB1,TAB2
from BasedOn_Col1_List t1 , BasedOn_Col2_List t2 where t1.Id=t2.id;
-- -- Preparing the final Result ----------------
While NoOFRowsInFinalResult<=NoOfColumnInTable2 do -- / Or NoOFRowsInFinalResult<=NoOfColumnInTable2 --
SET _Tab1 =(Select Table1Name from TableFromColumnList where Id=NoOFRowsInFinalResult);
SET _COLS1 =(Select Column_Name_Table1 from TableFromColumnList where Id=NoOFRowsInFinalResult);
SET _TAB2 =(Select Table2Name from TableFromColumnList where Id=NoOFRowsInFinalResult);
SET _COLS2 =(Select Column_Name_Table2 from TableFromColumnList where Id=NoOFRowsInFinalResult);
IF NoOFRowsInFinalResult=1 then
SET querystring =concat_ws("" , querystring,_Tab1,".", _COLS1 , "=",_Tab2,".", _COLS2," ");
else
SET querystring =concat_ws("" , querystring ,"and",_Tab1,".", _COLS1 , "=" ,_Tab2,".", _COLS2 ," ");
end if;
SET NoOFRowsInFinalResult=NoOFRowsInFinalResult+1 ;
End while;
SET querystring=concat_ws("","Select * from ",TAB1,", " ,TAB2," where ",querystring);
Select querystring;
END

Answer 3

CREATE PROCEDURE matchTables
#TAB1 VARCHAR(25),
#TAB2 VARCHAR(25),
#COLS1 VARCHAR(250) ,
#COLS2 VARCHAR(250)
AS
BEGIN
DECLARE #WHEREstring VARCHAR(MAX)
SET #WHEREstring =
'
WHERE
'
SELECT #WHEREstring = #WHEREstring + #TAB1 +'.'+ tab1.col+' = '+#TAB2+'.' + tab2.col +' AND
'
FROM
(
SELECT QUOTENAME(split.a.value('.','VARCHAR(100)')) AS col, ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS RowNum
FROM
(
SELECT Cast ('<M>' + Replace(#COLS1, '#', '</M><M>')+ '</M>' AS XML) AS Tab1Data
) AS A
CROSS apply Tab1Data.nodes ('/M') AS Split(a)
) tab1
INNER JOIN
(
Select QUOTENAME(AliasSplit.c.value('.', 'varchar(100)')) AS col, ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS RowNum
FROM
(
SELECT Cast ('<A>' + Replace(#COLS2, '#', '</A><A>')+ '</A>' AS XML) AS Tab2Data
) AS A
CROSS apply Tab2Data.nodes ('/A') AS AliasSplit(c)
) tab2
ON tab1.RowNum = tab2.RowNum
SET #WHEREstring= LEFT(#WHEREstring, LEN(#WHEREstring) - 8)
print #WHEREstring
END
Now, execute it using :::
EXEC matchTables 'table1', 'table2', 'col1#col2#col3#col4' , 'col2#col13#col1#col8'
i hope you got the desired where clause. cheers

Answer 4

You can build your own function:
CREATE FUNCTION String_split(inp VARCHAR(255),del VARCHAR(255),loc INT)
RETURNS VARCHAR(255)
RETURN REPLACE(Substring(Substring_index(inp, del,loc),LENGTH(Substring_index(inp, del, loc-1)) + 1),del, '');

Answer 5

CHAR_LENGTH - return correct length in chars
CREATE FUNCTION SPLIT_STR(
x VARCHAR(255),
delim VARCHAR(12),
pos INT
)
RETURNS VARCHAR(255)
RETURN REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos),
CHAR_LENGTH(SUBSTRING_INDEX(x, delim, pos -1)) + 1),
delim, '');