How to Build a Database query

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shaz 2012-4-2

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https://ww2.mathworks.cn/matlabcentral/answers/34225-how-to-build-a-database-query

Hi i have 3 variables one say Columnname tells about the database column names ,other two variable2 & variable3 tells about timestamp for eg( 03-Apr-2012 12:25:00 ).

Columnname = abcd variable2 = 03-Apr-2012 12:25:00 variable3 = 10-Apr-2012 12:25:00

after connecting to database & building query like this

data=exec(connection,'SELECT Columnname FROM TABLENMAE WHERE Columnname >= (''variable2 '') AND Columnname < (''variable3 '') ');

but i am getting data as blank.feels some issues while building query

Thanks in advance

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Answer 1

Titus Edelhofer 2012-4-2

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Hi,

it should probably read

data=exec(connection, ['SELECT ' Columnname ' FROM TABLENMAE WHERE ' Columnname '>=("' variable2 '") AND ' Columnname ' < ("' variable3 '") ']);

Two suggestions: it's easier if you do something like

sqlstatement = ['SELECT ...' ];
data = exec(connection, sqlstatement);

because then you can put a breakpoint on the exec line and see if your sqlstatement looks fine (e.g. copy paste to database client).

Second: use querybuilder to build your sql query ...

Titus

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shaz 2012-4-2

Thanks for replying..but have some issues while executing

??? No constructor 'com.mathworks.toolbox.database.sqlExec' with matching signature

found.

Error in ==> cursor.cursor at 60

curs.Cursor = com.mathworks.toolbox.database.sqlExec(curs.SQLQuery ,connect.Handle);

Error in ==> database.exec at 34

curs=cursor(connect,sqlQuery);

Titus Edelhofer 2012-4-2

Hi,

did you try the second? How does sqlstatement look like? Is it perhaps a cell array (because one of your variables is a cell array?). Then you would need to replace (e.g.) Columnname by Columnname{1} ...

Titus

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