You are now a sqlite data analyst, and you are given a database schema as follows:

    【Schema】
    【DB_ID】 european_football_2
【Schema】
# Table: League
[
(id:INTEGER, Primary Key, Examples: [1, 1729, 4769]),
(country_id:INTEGER, Examples: [1, 1729, 4769]),
(name:TEXT, Examples: [Belgium Jupiler League])
]
# Table: Match
[
(id:INTEGER, Primary Key, Examples: [4769, 4770, 4771]),
(country_id:INTEGER, Examples: [1, 1729, 4769]),
(league_id:INTEGER, Examples: [1, 1729, 4769]),
(season:TEXT, Examples: [2008/2009, 2009/2010, 2010/2011]),
(stage:INTEGER, Examples: [1, 10, 11]),
(date:TEXT, Examples: [2008-08-17 00:00:00, 2008-08-16 00:00:00, 2008-09-24 00:00:00]),
(match_api_id:INTEGER, Examples: [483129, 483130, 483131]),
(home_team_api_id:INTEGER, Examples: [9987, 10000, 9984]),
(away_team_api_id:INTEGER, Examples: [9993, 9994, 8635]),
(home_team_goal:INTEGER, Examples: [1, 0, 5]),
(away_team_goal:INTEGER, Examples: [1, 0, 3]),
(home_player_X1:INTEGER, Examples: [1, 2, 0]),
(home_player_X2:INTEGER, Examples: [2, 4, 3]),
(home_player_X3:INTEGER, Examples: [4, 6, 8]),
(home_player_X4:INTEGER, Examples: [6, 8, 4]),
(home_player_X5:INTEGER, Examples: [8, 6, 2]),
(home_player_X6:INTEGER, Examples: [2, 6, 4]),
(home_player_X7:INTEGER, Examples: [4, 8, 6]),
(home_player_X8:INTEGER, Examples: [6, 2, 8]),
(home_player_X9:INTEGER, Examples: [8, 4, 2]),
(home_player_X10:INTEGER, Examples: [4, 6, 9]),
(home_player_X11:INTEGER, Examples: [6, 4, 5]),
(away_player_X1:INTEGER, Examples: [1, 2, 6]),
(away_player_X2:INTEGER, Examples: [2, 4, 3]),
(away_player_X3:INTEGER, Examples: [4, 6, 5]),
(away_player_X4:INTEGER, Examples: [6, 8, 2]),
(away_player_X5:INTEGER, Examples: [8, 6, 4]),
(away_player_X6:INTEGER, Examples: [2, 4, 3]),
(away_player_X7:INTEGER, Examples: [4, 6, 5]),
(away_player_X8:INTEGER, Examples: [6, 8, 7]),
(away_player_X9:INTEGER, Examples: [8, 2, 6]),
(away_player_X10:INTEGER, Examples: [4, 6, 7]),
(away_player_X11:INTEGER, Examples: [6, 4, 3]),
(home_player_Y1:INTEGER, Examples: [1, 3, 0]),
(home_player_Y2:INTEGER, Examples: [3, 0]),
(home_player_Y3:INTEGER, Examples: [3, 5]),
(home_player_Y4:INTEGER, Examples: [3, 5]),
(home_player_Y5:INTEGER, Examples: [3, 7, 6]),
(home_player_Y6:INTEGER, Examples: [7, 3, 6]),
(home_player_Y7:INTEGER, Examples: [7, 6, 8]),
(home_player_Y8:INTEGER, Examples: [7, 8, 6]),
(home_player_Y9:INTEGER, Examples: [7, 10, 8]),
(home_player_Y10:INTEGER, Examples: [10, 7, 8]),
(home_player_Y11:INTEGER, Examples: [10, 11, 1]),
(away_player_Y1:INTEGER, Examples: [1, 3]),
(away_player_Y2:INTEGER, Examples: [3]),
(away_player_Y3:INTEGER, Examples: [3, 7]),
(away_player_Y4:INTEGER, Examples: [3, 5, 7]),
(away_player_Y5:INTEGER, Examples: [3, 7, 6]),
(away_player_Y6:INTEGER, Examples: [7, 3, 6]),
(away_player_Y7:INTEGER, Examples: [7, 6, 8]),
(away_player_Y8:INTEGER, Examples: [7, 8, 6]),
(away_player_Y9:INTEGER, Examples: [7, 10, 8]),
(away_player_Y10:INTEGER, Examples: [10, 7, 8]),
(away_player_Y11:INTEGER, Examples: [10, 11, 8]),
(home_player_1:INTEGER, Examples: [39890, 38327, 95597]),
(home_player_2:INTEGER, Examples: [67950, 39580, 38292]),
(home_player_3:INTEGER, Examples: [38788, 67958, 30692]),
(home_player_4:INTEGER, Examples: [38312, 67959, 38435]),
(home_player_5:INTEGER, Examples: [26235, 37112, 94462]),
(home_player_6:INTEGER, Examples: [36393, 46004, 119117]),
(home_player_7:INTEGER, Examples: [148286, 164732, 35412]),
(home_player_8:INTEGER, Examples: [67898, 39631, 95609]),
(home_player_9:INTEGER, Examples: [26916, 164352, 38246]),
(home_player_10:INTEGER, Examples: [38801, 38423, 25957]),
(home_player_11:INTEGER, Examples: [94289, 26502, 38419]),
(away_player_1:INTEGER, Examples: [34480, 37937, 38252]),
(away_player_2:INTEGER, Examples: [38388, 38293, 39156]),
(away_player_3:INTEGER, Examples: [26458, 148313, 39151]),
(away_player_4:INTEGER, Examples: [13423, 104411, 166554]),
(away_player_5:INTEGER, Examples: [38389, 148314, 15652]),
(away_player_6:INTEGER, Examples: [38798, 37202, 39145]),
(away_player_7:INTEGER, Examples: [30949, 43158, 46890]),
(away_player_8:INTEGER, Examples: [38253, 9307, 38947]),
(away_player_9:INTEGER, Examples: [106013, 42153, 46881]),
(away_player_10:INTEGER, Examples: [38383, 32690, 39158]),
(away_player_11:INTEGER, Examples: [46552, 38782, 119118]),
(goal:TEXT),
(shoton:TEXT),
(shotoff:TEXT),
(foulcommit:TEXT),
(card:TEXT),
(cross:TEXT),
(corner:TEXT),
(possession:TEXT),
(B365H:REAL, Examples: [1.73, 1.95, 2.38]),
(B365D:REAL, Examples: [3.4, 3.2, 3.3]),
(B365A:REAL, Examples: [5.0, 3.6, 2.75]),
(BWH:REAL, Examples: [1.75, 1.8, 2.4]),
(BWD:REAL, Examples: [3.35, 3.3, 4.0]),
(BWA:REAL, Examples: [4.2, 3.95, 2.55]),
(IWH:REAL, Examples: [1.85, 1.9, 2.6]),
(IWD:REAL, Examples: [3.2, 3.1, 3.9]),
(IWA:REAL, Examples: [3.5, 2.3, 6.0]),
(LBH:REAL, Examples: [1.8, 1.9, 2.5]),
(LBD:REAL, Examples: [3.3, 3.2, 3.6]),
(LBA:REAL, Examples: [3.75, 3.5, 2.5]),
(PSH:REAL, Examples: [5.1, 2.48, 1.83]),
(PSD:REAL, Examples: [3.82, 3.52, 3.79]),
(PSA:REAL, Examples: [1.76, 2.96, 4.63]),
(WHH:REAL, Examples: [1.7, 1.83, 2.5]),
(WHD:REAL, Examples: [3.3, 3.25, 3.75]),
(WHA:REAL, Examples: [4.33, 3.6, 2.4]),
(SJH:REAL, Examples: [1.9, 1.95, 2.63]),
(SJD:REAL, Examples: [3.3, 4.0, 3.5]),
(SJA:REAL, Examples: [4.0, 3.8, 2.5]),
(VCH:REAL, Examples: [1.65, 2.0, 2.35]),
(VCD:REAL, Examples: [3.4, 3.25, 3.75]),
(VCA:REAL, Examples: [4.5, 3.25, 2.65]),
(GBH:REAL, Examples: [1.78, 1.85, 2.5]),
(GBD:REAL, Examples: [3.25, 3.2, 3.75]),
(GBA:REAL, Examples: [4.0, 3.75, 2.5]),
(BSH:REAL, Examples: [1.73, 1.91, 2.3]),
(BSD:REAL, Examples: [3.4, 3.25, 3.2]),
(BSA:REAL, Examples: [4.2, 3.6, 2.75])
]
# Table: Team_Attributes
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(team_fifa_api_id:INTEGER, Examples: [434, 77, 614]),
(team_api_id:INTEGER, Examples: [9930, 8485, 8576]),
(date:TEXT, Examples: [2010-02-22 00:00:00, 2014-09-19 00:00:00, 2015-09-10 00:00:00]),
(buildUpPlaySpeed:INTEGER, Examples: [60, 52, 47]),
(buildUpPlaySpeedClass:TEXT, Examples: [Balanced, Fast, Slow]),
(buildUpPlayDribbling:INTEGER, Examples: [48, 41, 64]),
(buildUpPlayDribblingClass:TEXT, Examples: [Little, Normal, Lots]),
(buildUpPlayPassing:INTEGER, Examples: [50, 56, 54]),
(buildUpPlayPassingClass:TEXT, Examples: [Mixed, Long, Short]),
(buildUpPlayPositioningClass:TEXT, Examples: [Organised, Free Form]),
(chanceCreationPassing:INTEGER, Examples: [60, 54, 70]),
(chanceCreationPassingClass:TEXT, Examples: [Normal, Risky, Safe]),
(chanceCreationCrossing:INTEGER, Examples: [65, 63, 70]),
(chanceCreationCrossingClass:TEXT, Examples: [Normal, Lots, Little]),
(chanceCreationShooting:INTEGER, Examples: [55, 64, 70]),
(chanceCreationShootingClass:TEXT, Examples: [Normal, Lots, Little]),
(chanceCreationPositioningClass:TEXT, Examples: [Organised, Free Form]),
(defencePressure:INTEGER, Examples: [50, 47, 60]),
(defencePressureClass:TEXT, Examples: [Medium, Deep, High]),
(defenceAggression:INTEGER, Examples: [55, 44, 70]),
(defenceAggressionClass:TEXT, Examples: [Press, Double, Contain]),
(defenceTeamWidth:INTEGER, Examples: [45, 54, 70]),
(defenceTeamWidthClass:TEXT, Examples: [Normal, Wide, Narrow]),
(defenceDefenderLineClass:TEXT, Examples: [Cover, Offside Trap])
]
# Table: Country
[
(id:INTEGER, Primary Key, Examples: [1, 1729, 4769]),
(name:TEXT, Examples: [Belgium, England, France])
]
# Table: Team
[
(id:INTEGER, Primary Key, Examples: [31446, 1513, 31456]),
(team_api_id:INTEGER, Examples: [1601, 1773, 1957]),
(team_fifa_api_id:INTEGER, Examples: [673, 675, 15005]),
(team_long_name:TEXT, Examples: [KRC Genk, Beerschot AC, SV Zulte-Waregem]),
(team_short_name:TEXT, Examples: [GEN, BAC, ZUL])
]
# Table: Player_Attributes
[
(id:INTEGER, Primary Key, Examples: [1, 2, 3]),
(player_fifa_api_id:INTEGER, Examples: [218353, 189615, 186170]),
(player_api_id:INTEGER, Examples: [505942, 155782, 162549]),
(date:TEXT, Examples: [2016-02-18 00:00:00, 2015-11-19 00:00:00, 2015-09-21 00:00:00]),
(overall_rating:INTEGER, Examples: [67, 62, 61]),
(potential:INTEGER, Examples: [71, 66, 65]),
(preferred_foot:TEXT, Examples: [right, left]),
(attacking_work_rate:TEXT, Examples: [medium, high, low]),
(defensive_work_rate:TEXT, Examples: [medium, high, low]),
(crossing:INTEGER, Examples: [49, 48, 80]),
(finishing:INTEGER, Examples: [44, 43, 53]),
(heading_accuracy:INTEGER, Examples: [71, 70, 58]),
(short_passing:INTEGER, Examples: [61, 60, 71]),
(volleys:INTEGER, Examples: [44, 43, 40]),
(dribbling:INTEGER, Examples: [51, 50, 73]),
(curve:INTEGER, Examples: [45, 44, 70]),
(free_kick_accuracy:INTEGER, Examples: [39, 38, 69]),
(long_passing:INTEGER, Examples: [64, 63, 68]),
(ball_control:INTEGER, Examples: [49, 48, 71]),
(acceleration:INTEGER, Examples: [60, 79, 80]),
(sprint_speed:INTEGER, Examples: [64, 78, 82]),
(agility:INTEGER, Examples: [59, 78, 79]),
(reactions:INTEGER, Examples: [47, 46, 67]),
(balance:INTEGER, Examples: [65, 90, 87]),
(shot_power:INTEGER, Examples: [55, 54, 71]),
(jumping:INTEGER, Examples: [58, 85, 84]),
(stamina:INTEGER, Examples: [54, 79, 80]),
(strength:INTEGER, Examples: [76, 56, 50]),
(long_shots:INTEGER, Examples: [35, 34, 62]),
(aggression:INTEGER, Examples: [71, 63, 62]),
(interceptions:INTEGER, Examples: [70, 41, 40]),
(positioning:INTEGER, Examples: [45, 44, 60]),
(vision:INTEGER, Examples: [54, 53, 66]),
(penalties:INTEGER, Examples: [48, 47, 59]),
(marking:INTEGER, Examples: [65, 62, 76]),
(standing_tackle:INTEGER, Examples: [69, 66, 63]),
(sliding_tackle:INTEGER, Examples: [69, 66, 78]),
(gk_diving:INTEGER, Examples: [6, 5, 14]),
(gk_handling:INTEGER, Examples: [11, 10, 7]),
(gk_kicking:INTEGER, Examples: [10, 9, 8]),
(gk_positioning:INTEGER, Examples: [8, 7, 9]),
(gk_reflexes:INTEGER, Examples: [8, 7, 12])
]
# Table: Player
[
(id:INTEGER, Primary Key, Examples: [3879, 401, 9179]),
(player_api_id:INTEGER, Examples: [2625, 2752, 2768]),
(player_name:TEXT, Examples: [Aaron Appindangoye, Aaron Cresswell, Aaron Doran]),
(player_fifa_api_id:INTEGER, Examples: [2, 6, 11]),
(birthday:TEXT, Examples: [1992-02-29 00:00:00, 1989-12-15 00:00:00, 1991-05-13 00:00:00]),
(height:INTEGER, Examples: [182.88, 170.18, 172.72]),
(weight:INTEGER, Examples: [187, 146, 163])
]
【Foreign keys】
League.country_id=country.id
Match.away_player_11=Player.player_api_id
Match.away_player_10=Player.player_api_id
Match.away_player_9=Player.player_api_id
Match.away_player_8=Player.player_api_id
Match.away_player_7=Player.player_api_id
Match.away_player_6=Player.player_api_id
Match.away_player_5=Player.player_api_id
Match.away_player_4=Player.player_api_id
Match.away_player_3=Player.player_api_id
Match.away_player_2=Player.player_api_id
Match.away_player_1=Player.player_api_id
Match.home_player_11=Player.player_api_id
Match.home_player_10=Player.player_api_id
Match.home_player_9=Player.player_api_id
Match.home_player_8=Player.player_api_id
Match.home_player_7=Player.player_api_id
Match.home_player_6=Player.player_api_id
Match.home_player_5=Player.player_api_id
Match.home_player_4=Player.player_api_id
Match.home_player_3=Player.player_api_id
Match.home_player_2=Player.player_api_id
Match.home_player_1=Player.player_api_id
Match.away_team_api_id=Team.team_api_id
Match.home_team_api_id=Team.team_api_id
Match.league_id=League.id
Match.country_id=Country.id
Team_Attributes.team_api_id=Team.team_api_id
Team_Attributes.team_fifa_api_id=Team.team_fifa_api_id
Player_Attributes.player_api_id=Player.player_api_id
Player_Attributes.player_fifa_api_id=Player.player_fifa_api_id

    【Question】
    What is the average overall rating of the players born before the year 1986? average overall rating = DIVIDE(SUM(overall_rating), COUNT(id)); born before the year 1986 refers to strftime('%Y', birthday) < '1986';

    【Evidence】
    average overall rating = DIVIDE(SUM(overall_rating), COUNT(id)); born before the year 1986 refers to strftime('%Y', birthday) < '1986';

    Please read and understand the database schema carefully, and generate an executable SQL based on the user's question and evidence. 

SQL: SELECT SUM(t2.overall_rating) / COUNT(t1.id) FROM Player AS t1 INNER JOIN Player_Attributes AS t2 ON t1.player_api_id = t2.player_api_id WHERE SUBSTR(t1.birthday, 1, 4) < '1986'