How to add condition to changeSet - liquibase

Question

I created database ChangeLog for liquibase and I have "CREATE TABLE" query.
I want to add condition to column "STATUS".
<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog
http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.5.xsd">
<changeSet id="1" author="xxx">
<comment>Create Asset table</comment>
<sql>
CREATE TABLE `TASK`(
`TASK_ID` bigint(20) NOT NULL,
`STATUS` VARCHAR(10), //(where status not equal to "pending")
`FILE_ID` varchar(100),
PRIMARY KEY (`DOC_ID`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
</sql>
</changeSet>
</databaseChangeLog>

Answer 1

If you want to update the columns datatype depending on certain conditions, you can use <preConditions> with <sqlCheck>, and then use <modifyDataType>.
So supposing that there's already a table with name TASK and it contains a column named STATUS, you can modify it's datatype as such:
<changeSet id="1" author="xxx">
<comment>Update Asset table</comment>
<preConditions onFail="MARK_RAN">
<and>
<columnExists tableName="TASK" columnName="STATUS"/>
<sqlCheck expectedResult="0"> SELECT COUNT(*) FROM TASK WHERE STATUS = "pending";</sqlCheck>
</and>
</preConditions>
<modifyDataType tableName="TASK" columnName="STATUS" newDataType="VARCHAR(10)"/>
</changeSet>
Or perhaps you'd like another onFail-behaviour. Check out this link
HALT - Immediately halt execution of entire change log [default]
CONTINUE - Skip over change set. Execution of change set will be
attempted again on the next update. Continue with change log.
MARK_RAN - Skip over change set, but mark it as ran. Continue with
change log
WARN - Output warning and continue executing change set as normal.