CREATE LOGIN newDbAdmin WITH password='123isTheBestPasswordEver'
CREATE USER newDbAdmin

DROP USER oldAdmin
DROP LOGIN oldAdmin

-- in master
create login [XXXX] with password = 'YYYYY'
create user [XXXX] from login [XXXX];

-- if you want the user to be able to create databases and logins
exec sp_addRoleMember 'dbmanager', 'XXXX';
exec sp_addRoleMember 'loginmanager', 'XXXX'

-- in each individual database, to grant dbo
create user [XXXX] from login [XXXX];
exec sp_addRoleMember 'db_owner', 'XXXX';

$newSqlUser = 'YOUR_NEW_LOGIN_HERE';
$serverName = 'YOUR-SERVER-NAME.database.windows.net'
$sqlAdminLogin = 'YOUR-ADMIN-SQL-LOGIN'
$createAdminUser = $TRUE;

# generate a nice long random password
Add-Type -Assembly System.Web
$newSqlPassword = [Web.Security.Membership]::GeneratePassword(25,3) -Replace '[%&+=;:/]', "!";

# prompt for your server admin password.
# Don't need the username param here but can be nice to avoid retyping
$sqlCreds = get-Credential -Username $sqlAdminLogin -Message 'Enter admin sql credentials'

# Create login and user in master db
$sql = "create login [$newSqlUser] with password = '$newSqlPassword'; create user [$newSqlUser] from login [$newSqlUser];"
invoke-sqlcmd -Query $sql -ServerInstance $serverName -Database 'master' -Username $sqlCreds.UserName -Password ( $sqlCreds.GetNetworkCredential().Password )
"new login: $newSqlUser"
"password: $newSqlPassword"

# sql to create user in each db
if ( $createAdminUser ) { `
    $createUserSql = "create user [$newSqlUser] from login [$newSqlUser]; exec sp_addRoleMember 'db_owner', '$newSqlUser'; "; `
} else { `
    $createUserSql = "create user [$newSqlUser] from login [$newSqlUser]; exec sp_addRoleMember 'db_datareader', '$newSqlUser'; exec sp_addRoleMember 'db_denydatawriter', '$newSqlUser';"; `
}

# can't have multiple Invoke-SQLCmd in a pipeline so get the dbnames first, then iterate
$sql = "select name from sys.databases where  name <> 'master';"
$dbNames = @()
invoke-sqlcmd -Query $sql -ServerInstance $serverName -Database 'master' -Username $sqlCreds.UserName -Password ( $sqlCreds.GetNetworkCredential().Password ) | `
   foreach { $dbNames += $_.name }
# iterate over the dbs and add user to each one
foreach ($db in $dbNames ) { `
       invoke-sqlcmd -Query $createUserSql -ServerInstance $serverName -Database $db -Username ($sqlCreds.UserName) -Password $( $sqlCreds.GetNetworkCredential().Password ); `
      "created user in $db database"; `
}