I have a db upgrade script to remove the non-null constraint on a column. I want to do a precondition check, and call ALTER TABLE
only when it is non-null.
The master.xml script is a progressive one where I keep adding scripts and the entire thing runs everytime. After the first time my Alter Table script has run, I do not want it to be run again.
Couldn't find a predefined precondition for this, and could not write an sqlcheck either.
Can be done with sqlCheck.
For MySql
<preConditions onFail="MARK_RAN" onError="CONTINUE">
<sqlCheck expectedResult="NO">
SELECT is_Nullable
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name='<table_name>'
AND column_name='<column_name>'
</sqlCheck>
</preConditions>
For Oracle:
<preConditions onFail="MARK_RAN" onError="CONTINUE">
<sqlCheck expectedResult="N">
SELECT Nullable
FROM user_tab_columns
WHERE table_name = '<table_name>'
AND column_name = '<column_name>'
</sqlCheck>
</preConditions>
For SQL Server:
<preConditions onFail="MARK_RAN" onError="CONTINUE">
<sqlCheck expectedResult="0">
SELECT is_nullable
FROM sys.columns
WHERE object_id = OBJECT_ID('<table_name>')
AND name = '<column_name>'
</sqlCheck>
</preConditions>