3.5 Ejercicios SQL con RSQLite
3.5.1 Setup de RSQLite
Vamos a utilizar RSQLite desde Kaggle. Pero si lo queréis instalar en local La información para su instalación está en el siguiente enlace.
library(DBI)
# Create an ephemeral in-memory RSQLite database
con <- dbConnect(RSQLite::SQLite(), ":memory:")
dbListTables(con)## character(0)## [1] "mtcars"## [1] "mpg" "cyl" "disp" "hp" "drat" "wt" "qsec" "vs" "am" "gear"
## [11] "carb"## mpg cyl disp hp drat wt qsec vs am gear carb
## 1 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4
## 2 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4
## 3 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
## 4 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1
## 5 18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2
## 6 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1
## 7 14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4
## 8 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
## 9 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
## 10 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4
## 11 17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4
## 12 16.4 8 275.8 180 3.07 4.070 17.40 0 0 3 3
## 13 17.3 8 275.8 180 3.07 3.730 17.60 0 0 3 3
## 14 15.2 8 275.8 180 3.07 3.780 18.00 0 0 3 3
## 15 10.4 8 472.0 205 2.93 5.250 17.98 0 0 3 4
## 16 10.4 8 460.0 215 3.00 5.424 17.82 0 0 3 4
## 17 14.7 8 440.0 230 3.23 5.345 17.42 0 0 3 4
## 18 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
## 19 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
## 20 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
## 21 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
## 22 15.5 8 318.0 150 2.76 3.520 16.87 0 0 3 2
## 23 15.2 8 304.0 150 3.15 3.435 17.30 0 0 3 2
## 24 13.3 8 350.0 245 3.73 3.840 15.41 0 0 3 4
## 25 19.2 8 400.0 175 3.08 3.845 17.05 0 0 3 2
## 26 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
## 27 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
## 28 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
## 29 15.8 8 351.0 264 4.22 3.170 14.50 0 1 5 4
## 30 19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6
## 31 15.0 8 301.0 335 3.54 3.570 14.60 0 1 5 8
## 32 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2# You can fetch all results:
res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
dbFetch(res)## mpg cyl disp hp drat wt qsec vs am gear carb
## 1 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
## 2 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
## 3 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
## 4 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
## 5 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
## 6 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
## 7 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
## 8 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
## 9 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
## 10 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
## 11 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2dbClearResult(res)
# Or a chunk at a time
res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
while(!dbHasCompleted(res)){
chunk <- dbFetch(res, n = 5)
print(nrow(chunk))
}## [1] 5
## [1] 5
## [1] 1