Bigquery - 如何将float浮动到字符串w/o向上/向下舍入？

Question

基本上我有一批GPS坐标（lat和long），我想要一个格式为“lat; long”的字符串。我所做的是：

CONCAT(CAST(Latitude AS STRING),";", CAST(Longitude AS STRING)) 

但遇到了一个问题，坐标由CAST（STRING（）做了同样的事情）四舍五入。例如，通过select CAST(45.3618927 as STRING)我会得到45.3619。我怎样才能防止这个四舍五入？

注意：我知道标准SQL中的SAFE_CAST给了我想要的东西，但由于其他原因，我不得不继续使用Legacy方言。

Answer 1

#legacySQL 
SELECT CONCAT(
    RTRIM(CONCAT(LEFT(lat_temp, lat_pos - 1), '.', SUBSTR(lat_temp, lat_pos)), '0'), 
    ';', 
    RTRIM(CONCAT(LEFT(lon_temp, lon_pos - 1), '.', SUBSTR(lon_temp, lon_pos)), '0') 
) AS lat_lon 
FROM (
    SELECT 
    INSTR(STRING(lat * 1000000), '.') - 6 AS lat_pos, 
    REPLACE(STRING(lat * 1000000),'.', '') AS lat_temp, 
    INSTR(STRING(lon * 1000000), '.') - 6 AS lon_pos, 
    REPLACE(STRING(lon * 1000000),'.', '') AS lon_temp 
    FROM 
    (SELECT 34.052235 AS lat, -118.243683 AS lon) AS yourTable 
) 

看起来很丑陋，但正如你所说 - 由于某种原因你要坚持wirg传统的SQL
否则请参阅下面的标准SQL版本

#standardSQL 
WITH yourTable AS (
    SELECT 34.052235 AS lat, -118.243683 AS lon 
) 
SELECT CONCAT(CAST(lat AS STRING),";", CAST(lon AS STRING)) AS lat_lon 
FROM yourTable 

另（较小丑陋的）版本对于Legacy SQL使用的是JS UDF

#legacySQL 
SELECT lat, lon, lat_lon 
FROM (JS(
    -- input table 
    (
    SELECT lat, lon FROM 
    (SELECT 34.052235 AS lat, -118.243683 AS lon) AS yourTable 
), 
    -- input vars 
    lat, lon, 
    -- output schema 
    "[ 
    {name: 'lat_lon', type: 'STRING'}, 
    {name: 'lat', type: 'FLOAT'}, 
    {name: 'lon', type: 'FLOAT'} 
    ]", 
    -- the function 
    "function(row, emit) { 
    emit({ 
     lat_lon: row.lat.toString().concat(';').concat(row.lon.toString()), 
     lat: row.lat, 
     lon: row.lon 
    }) 
    }" 
)) 

最后，如果碰巧 - 你将决定迁移到Standard SQL，使用FORMAT使生活变得更加容易（感谢艾略特的评论此）

#standardSQL 
SELECT FORMAT('%t;%t', lat, lon) AS lat_lon 
FROM 
    (SELECT 34.052235 AS lat, -118.243683 AS lon) AS yourTable