Question: I am new to MySQL trigger. I want to make a trigger that before the update is made from my `emp_audit` table will check first if the `empno` from my employees table already exists. If it exists then do the update otherwise do nothing.

I encounter the following error:

> 
> Error 1064
> 
> 
> 

The code is:

```
DELIMITER $$

CREATE TRIGGER before_emp_audit_update
BEFORE UPDATE ON emp_audit
FOR EACH ROW BEGIN 

  IF (SELECT COUNT(*) FROM employees WHERE empno = NEW.empno) = 1
  THEN
  UPDATE INTO emp_audit
  SET ACTION = 'update',
  empno = NEW.empno,
  lastname = NEW.lastname,
  changedat = NOW();

  END IF;
END$$
DELIMITER;

```

Answer: 
I had the same problem. It seems that SIRF and SURF are [no longer available in opencv > 3.4.2.16](https://github.com/DynaSlum/satsense/issues/13). I chose an older opencv-python and opencv-contrib-python versions and solved this problem. Here is the [history version](https://pypi.org/project/opencv-python/#history) about opencv-python, and I use the following code :

```
pip install opencv-python==3.4.2.16
pip install opencv-contrib-python==3.4.2.16

```

**Edit**

For Anaconda User just this instead of pip 

```
conda install -c menpo opencv

```

this will install cv2 3.4.1 and everything you need to run SIFT

good luck~
It may be due to a mismatch of opencv version and opencv-contrib version.
If you installed opencv from the source using CMake, and the source version is different from the version of opencv-contrib-python, uninstall the current opencv-contrib-python and do `pip install opencv-contrib-python==<version of the source>.X` or an another compatible version.
One version setup that I have running is opencv source (3.2), opencv-python (3.4.0.14) and opencv-contrib-python (3.4.2.17)