Getting Started with Liquibase and JSON on Linux and macOS

After you install Liquibase, get started with our tutorial and learn how Liquibase works.

With Liquibase, SQL statements [1] are declared as Liquibase changesets [2] in a changelog file [3].

Liquibase [4] then uses the changelog to apply the changesets to target databases [5].

In this tutorial, you will use an example changelog to apply two rounds of updates to an H2 database that is included with the Liquibase installation files.

Applying updates to the database

  1. Copy the Liquibase /examples directory from the installation directory to another location on your machine.
  2. From a command line terminal, enter <your path>/examples/start-h2 to start the example H2 database. The database console opens automatically in a browser on port 9090.
  3. Open a new command line terminal and enter the following commands:
  4. cd <your path>/examples/json
    liquibase update

    Note: When prompted about the operation's report in Liquibase Hub, enter S to skip for now.

    Liquibase applies the following updates, which are specified as Liquibase changesets in example-changelog.json.

    "changeSet": {
      "id": "1",
      "author": "your.name",
      "changes": [
        {
          "createTable": {
            "tableName": "person",
            "columns": [
              {
                "column": {
                  "name": "id",
                  "type": "int",
                  "autoIncrement": true,
                  "constraints": {
    	            "primaryKey": true,
    		        "nullable": false
    	          },
    	        }
              },
              {
    	        "column": {
                  "name": "name",
    	          "type": "varchar(50)"
                }
              },
    	      {
    	        "column": {
    	          "name": "addresss1",
                  "type": "varchar(50)"
    	        }
    	      },
    	      {
    	        "column": {
                  "name": "addresss2",
    	          "type": "varchar(50)"
    	        }
    	      },
    	      {
                "column": {
                  "name": "city",
                  "type": "varchar(30)"									
    	        }
              }
            ]
          }
        }]
      }
    },
    {
      "changeSet": {
        "id": "2",
        "author": "your.name",
        "changes": [
          {
            "createTable": {
    	      "tableName": "company",
    	      "columns": [
    	        {
    	          "column": {
                    "name": "id",
                    "type": "int",
                    "autoIncrement": true,
                    "constraints": {
                      "primaryKey": true,
                      "nullable": false
    		        },
    	          }
    	        },
    	        { 
    	          "column": {
    	            "name": "name",
    	            "type": "varchar(50)"
                  }									
    	        },
                {
    	          "column": {
                    "name": "addresss1",
    	            "type": "varchar(50)"
    	          }
    	        },
    	        {
    	          "column": {
                    "name": "addresss2",
    		        "type": "varchar(50)"
    	          }
    	        },
                {
    	          "column": {
                    "name": "city",
                    "type": "varchar(30)"
    	          }
    	        }
    	      ]
            }
          }]
        }
      },	
      {
        "changeSet": {
          "id": "3",
          "author": "your.name",
          "changes": [
            {
              "addColumn": {
                "tableName": "company",
                "columns": [
                  {
                    "column": {
                      "name": "country",
                      "type": "varchar(2)"
                    }
                  }
                ]
              }
            }]
          }

    The author-id value pairs your.name:1 and your.name:2 prevent their respective changesets from accidentally being run multiple times as new changesets are added to the changelog for subsequent updates.

  1. From the database console, confirm that the Object view contains the COMPANY and PERSON tables that were created during the previous step.
  1. Using a text editor, open <your path>/examples/json/example-changelog.json, add a comma after the last changeset closing braces }, and then add the following changesets to the end of the file before ]}:
  2. {
      "changeSet": {
        "id": "4",
        "author": "your.name",
        "changes": [
          {
            "addColumn": { 
              "tableName": "person",									
              "columns": [
                {
                  "column": {
                    "name": "country",
                    "type": "varchar(2)"
                  }
                }
              ]
            }
         }] 
       }
     }
  1. Save and close example-changelog.json.
  1. Enter the following command:
  2. liquibase update
  1. Confirm the update by refreshing the database console and verifying that the country column has been added to the PERSON table.

Next steps