I have newly setup TYPO3, but when I try to add/save content, it gives me this error:
SQL error: 'Incorrect integer value: '' for column 'sys_language_uid' at row 1
The behavior is related to database management systems using strict mode, like MySQL since version 5.7. Disabling strict mode (like provided in the accepted answer) is just a work around.
The real solution would be to explicitly cast values to integer by modifying TCA (table configuration array) for the according field definitions.
input
that would be setting/extending 'eval' => 'int'
, see example tt_content.starttime
'default' => 0
, see example tt_content.sys_language_uid