# MethodError: promote\_type error saving DataFrame to SQLite database

**URL:** <https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038>\
**Category:** General Usage\
**Created:** [November 25, 2021, 2:44am UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038 "2021-11-25T02:44:58Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![blackeneth](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/blackeneth/32/10353_2.png) [@blackeneth](https://discourse.julialang.org/u/blackeneth)\
**Post date:** [November 25, 2021, 2:44am UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038/1 "2021-11-25T02:44:58Z")

</div>

My apologies that the MWE example is somewhat involved to setup.

Overview: I’m loading a .csv file into a DataFrame, then I want to save that DataFrame to an SQLite database. I’m using Julia 1.6.2 (Windows).

Preliminaries:

```julia
using CSV
using DataFrames
using SQLite

```

Creating the database table:

```julia
   dbname="property.db"
   db = SQLite.DB(dbname)

    DBInterface.execute(db,"
    CREATE TABLE IF NOT EXISTS parcel (
        apn text not null,
        parcel text not null,
        acmna integer not null,
        arcadia integer not null,
        earcadia integer not null,
        triangle integer not null,
        camel integer not null,
        puc text,
        okmail integer not null,
        lat real,
        long real,
        PRIMARY KEY (apn)
        FOREIGN KEY (apn) 
            REFERENCES owner (apn)
            ON DELETE RESTRICT
            DEFERRABLE INITIALLY DEFERRED
        FOREIGN KEY (apn) 
            REFERENCES propertyinfo (apn)
            ON DELETE RESTRICT
            DEFERRABLE INITIALLY DEFERRED
        FOREIGN KEY (apn)
            REFERENCES residential (apn)
            ON DELETE RESTRICT
            DEFERRABLE INITIALLY DEFERRED
    );    
    ")

```

Here are a few rows of example data for the csv file, parcel-small.csv :

```julia
apn,parcel,acmna,arcadia,earcadia,triangle,camel,puc,okmail,lat,long
17347062C,173-47-062C,0,0,1,1,0,0131,1,33.49506748,-111.9380067
17347062B,173-47-062B,0,0,1,1,0,0131,1,33.49507362,-111.9376848
17347062A,173-47-062A,0,0,1,1,0,0151,1,33.49509066,-111.9373146
17347061,173-47-061,0,0,1,1,0,9700,0,33.49545436,-111.9351501
17347060,173-47-060,0,0,1,1,0,0131,1,33.49518552,-111.9367811
17347059,173-47-059,0,0,1,1,0,0131,1,33.49518982,-111.9364666

```

Here is the code to read the .csv into a DataFrame:

```julia
pint = Dict([("puc",String)])
df_small = CSV.File("parcel-small.csv";types=pint) |> DataFrame 

```

The data is read in and put into a dataframe:

```julia
 Row │ apn parcel acmna arcadia earcadia triangle camel puc okmail lat long
     │ String String Int64 Int64 Int64 Int64 Int64 String Int64 Float64 Float64  
─────┼──────────────────────────────────────────────────────────────────────────────────────────────────────
   1 │ 17347062C 173-47-062C 0 0 1 1 0 0131 1 33.4951 -111.938
   2 │ 17347062B 173-47-062B 0 0 1 1 0 0131 1 33.4951 -111.938
   3 │ 17347062A 173-47-062A 0 0 1 1 0 0151 1 33.4951 -111.937
   4 │ 17347061 173-47-061 0 0 1 1 0 9700 0 33.4955 -111.935
   5 │ 17347060 173-47-060 0 0 1 1 0 0131 1 33.4952 -111.937
   6 │ 17347059 173-47-059 0 0 1 1 0 0131 1 33.4952 -111.936

```

The .csv is read into the dataframe with the appropriate types, which match the types defined for the database table.

Now comes the step to save the DataFrame to the “parcel” table in the SQLite database:

```julia
ulia> Stat = SQLite.load!(df_small,db,"parcel")
ERROR: MethodError: promote_type(::Type{Union{}}, ::Type{String}) is ambiguous. Candidates:
  promote_type(::Type{Union{}}, ::Type{T}) where T in Base at promotion.jl:224
  promote_type(::Type{T}, ::Type{String}) where T<:WeakRefStrings.InlineString in WeakRefStrings at C:\Users\amgough\.julia\packages\WeakRefStrings\a3jYm\src\inlinestrings.jl:
44
Possible fix, define
  promote_type(::Type{Union{}}, ::Type{String})
Stacktrace:
  [1] add_or_widen!(val::String, col::Int64, nm::Symbol, dest::Tables.EmptyVector, row::Int64, updated::Base.RefValue{Any}, L::Base.SizeUnknown)
    @ Tables C:\Users\amgough\.julia\packages\Tables\gg6Id\src\fallbacks.jl:150
<more error lines>

```

Hmm… don’t know how to fix that. My DataFrame, and database, types are plain vanilla - Strings, Integers, and Float64.

---

<div class="post-metadata">

**Author:** ![blackeneth](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/blackeneth/32/10353_2.png) [@blackeneth](https://discourse.julialang.org/u/blackeneth)\
**Post date:** [November 27, 2021, 2:20am UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038/2 "2021-11-27T02:20:09Z")

</div>

To answer my own question …

Looking in promotions.jl in base, one can find the syntax for promote\_type

Adding this line eliminates the error

```julia
Base.promote_type(::Type{Union{}}, ::Type{String}) = String

```

Later, I got some additional variations of the same error. The complete set of fixes ended up being:

```julia
    Base.promote_type(::Type{Union{}}, ::Type{String}) = String
    Base.promote_type(::Type{Union{}}, ::AbstractString) = String
    Base.promote_type(::Type{Union{}}, ::String) = String

```

---

<div class="post-metadata">

**Author:** ![nalimilan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nalimilan/32/147_2.png) [@nalimilan](https://discourse.julialang.org/u/nalimilan)\
**Post date:** [November 27, 2021, 10:03pm UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038/3 "2021-11-27T22:03:42Z")

</div>

Which version of WeakRefStrings do you have? From the logs you posted it doesn’t seem to be the last one (1.4.1) and the bug doesn’t seem to happen with that version.

---

<div class="post-metadata">

**Author:** ![sransome](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sransome/32/29810_2.png) [@sransome](https://discourse.julialang.org/u/sransome)\
**Post date:** [December 10, 2021, 12:16am UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038/4 "2021-12-10T00:16:04Z")

</div>

I had the same issue with 1.7.0. My code was working fine, then I installed the MarketTechnicals package and from that point I have been unable to fix. I’m not skilled enough to understand the true underlying cause but your fix worked for me, thanks.

the code failing for me was…  
` df = DataFrame(DBInterface.execute(db, sql))`

I’m spending more time trying to solve this type of issue than coding recently so I’m getting very paranoid about adding new packaged or updating anything.

> [@blackeneth](#):
>
> ```julia
> Base.promote_type(::Type{Union{}}, ::Type{String}) = String
> Base.promote_type(::Type{Union{}}, ::AbstractString) = String
> Base.promote_type(::Type{Union{}}, ::String) = String
> 
> ```

---

<div class="post-metadata">

**Author:** ![pdeffebach](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pdeffebach/32/10320_2.png) [@pdeffebach](https://discourse.julialang.org/u/pdeffebach)\
**Post date:** [December 10, 2021, 1:49am UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038/5 "2021-12-10T01:49:04Z")

</div>

Can you post the output of `] st -m` So we can see what versions of packages you are running?

---

<div class="post-metadata">

**Author:** ![sransome](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sransome/32/29810_2.png) [@sransome](https://discourse.julialang.org/u/sransome)\
**Post date:** [December 10, 2021, 2:03am UTC](https://discourse.julialang.org/t/methoderror-promote-type-error-saving-dataframe-to-sqlite-database/72038/6 "2021-12-10T02:03:18Z")

</div>

Julia v 1.7.0  
Julia language support 1.5.6  
VScode  
Windows 10

```julia
using DataFrames
using DataFramesMeta
using Dates
using SQLite
using XLSX
using HTTP
using JSON
using FileIO
using Observables
using Colors
using Statistics, Random
using Missings
using CSV
using Indicators

```

[621f4979] AbstractFFTs v1.0.1  
[1520ce14] AbstractTrees v0.3.4  
[79e6a3ab] Adapt v3.3.1  
[27a7e980] Animations v0.4.1  
[4fba245c] ArrayInterface v3.2.1  
[67c07d97] Automa v0.8.2  
[13072b0f] AxisAlgorithms v1.0.1  
[b99e7846] BinaryProvider v0.5.10  
[fa961155] CEnum v0.4.1  
[336ed68f] CSV v0.9.11  
[8be319e6] Chain v0.4.10  
[d360d2e6] ChainRulesCore v1.11.2  
[9e997f8a] ChangesOfVariables v0.1.1  
[944b1d66] CodecZlib v0.7.0  
[a2cac450] ColorBrewer v0.4.0  
[35d6a980] ColorSchemes v3.15.0  
[3da002f7] ColorTypes v0.11.0  
[c3611d14] ColorVectorSpace v0.9.8  
[5ae59095] Colors v0.12.8  
[34da2185] Compat v3.40.0  
[d38c429a] Contour v0.5.7  
[a8cc5b0e] Crayons v4.0.4  
[a10d1c49] DBInterface v2.5.0  
[9a962f9c] DataAPI v1.9.0  
[a93c6f00] DataFrames v1.3.0  
[1313f7d8] DataFramesMeta v0.10.0  
[864edb3b] DataStructures v0.18.11  
[e2d170a0] DataValueInterfaces v1.0.0  
[b429d917] DensityInterface v0.4.0  
[31c24e10] Distributions v0.25.34  
[ffbed154] DocStringExtensions v0.8.6  
[da5c29d0] EllipsisNotation v1.1.3  
[8f5d6c58] EzXML v1.1.0  
[c87230d0] FFMPEG v0.4.1  
[7a1cc6ca] FFTW v1.4.5  
[5789e2e9] FileIO v1.11.2  
[48062228] FilePathsBase v0.9.17  
[1a297f60] FillArrays v0.12.7  
[53c48c17] FixedPointNumbers v0.8.4  
[59287772] Formatting v0.4.2  
[b38be410] FreeType v4.0.0  
[663a7486] FreeTypeAbstraction v0.9.5  
[f7f18e0c] GLFW v3.4.1  
[e9467ef8] GLMakie v0.4.7  
[5c1252a2] GeometryBasics v0.4.1  
[a2bd30eb] Graphics v1.1.1  
[3955a311] GridLayoutBase v0.6.4  
[42e2da0e] Grisu v1.0.2  
[cd3eb016] HTTP v0.9.17  
[615f187c] IfElse v0.1.1  
[a09fc81d] ImageCore v0.9.3  
[82e4d734] ImageIO v0.5.9  
[70c4c096] Indicators v0.8.1  
[9b13fd28] IndirectArrays v1.0.0  
[d25df0c9] Inflate v0.1.2  
[83e8ac13] IniFile v0.5.0  
[842dd82b] InlineStrings v1.1.0  
[a98d9a8b] Interpolations v0.13.4  
[8197267c] IntervalSets v0.5.3  
[3587e190] InverseFunctions v0.1.2  
[41ab1584] InvertedIndices v1.1.0  
[92d709cd] IrrationalConstants v0.1.1  
[f1662d9f] Isoband v0.1.1  
[c8e1da08] IterTools v1.4.0  
[82899510] IteratorInterfaceExtensions v1.0.0  
[692b3bcd] JLLWrappers v1.3.0  
[682c06a0] JSON v0.21.2  
[5ab0869b] KernelDensity v0.6.3  
[b964fa9f] LaTeXStrings v1.3.0  
[2ab3a3ac] LogExpFunctions v0.3.5  
[1914dd2f] MacroTools v0.5.9  
[ee78f7c6] Makie v0.15.3  
[20f20a25] MakieCore v0.1.3  
[dbb5928d] MappedArrays v0.4.1  
[7eb4fadd] Match v1.2.0  
[0a4f8689] MathTeXEngine v0.2.1  
[739be429] MbedTLS v1.0.3  
[7269a6da] MeshIO v0.4.9  
[e1d29d7a] Missings v1.0.2  
[66fc600b] ModernGL v1.1.3  
[e94cdb99] MosaicViews v0.3.3  
[77ba4419] NaNMath v0.3.5  
[f09324ee] Netpbm v1.0.2  
[510215fc] Observables v0.4.0  
[6fe1bfb0] OffsetArrays v1.10.8  
[52e1d378] OpenEXR v0.3.2  
[bac558e1] OrderedCollections v1.4.1  
[90014a1f] PDMats v0.11.5  
[f57f5aa1] PNGFiles v0.3.12  
[19eb6ba3] Packing v0.4.2  
[5432bcbf] PaddedViews v0.5.10  
[69de0a69] Parsers v2.1.2  
[eebad327] PkgVersion v0.1.1  
[995b91a9] PlotUtils v1.0.15  
[647866c9] PolygonOps v0.1.2  
[2dfb63ee] PooledArrays v1.4.0  
[21216c6a] Preferences v1.2.2  
[08abe8d2] PrettyTables v1.2.3  
[92933f4c] ProgressMeter v1.7.1  
[1fd47b50] QuadGK v2.4.2  
[c84ed2f1] Ratios v0.4.2  
[3cdcf5f2] RecipesBase v1.2.1  
[189a3867] Reexport v1.2.2  
[05181044] RelocatableFolders v0.1.3  
[ae029012] Requires v1.1.3  
[79098fc4] Rmath v0.7.0  
[fdea26ae] SIMD v3.3.1  
[0aa819cd] SQLite v1.3.0  
[7b38b023] ScanByte v0.3.0  
[6c6a2e73] Scratch v1.1.0  
[91c51154] SentinelArrays v1.3.8  
[65257c39] ShaderAbstractions v0.2.8  
[992d4aef] Showoff v1.0.3  
[73760f76] SignedDistanceFields v0.4.0  
[a2af1166] SortingAlgorithms v1.0.1  
[276daf66] SpecialFunctions v1.8.1  
[cae243ae] StackViews v0.1.1  
[aedffcd0] Static v0.4.0  
[90137ffa] StaticArrays v1.2.13  
[82ae8749] StatsAPI v1.1.0  
[2913bbd2] StatsBase v0.33.13  
[4c63d2b9] StatsFuns v0.9.14  
[09ab397b] StructArrays v0.6.3  
[3783bdb8] TableTraits v1.0.1  
[bd369af6] Tables v1.6.0  
[a110ec8f] Temporal v0.8.1  
[62fd8b95] TensorCore v0.1.1  
[731e570b] TiffImages v0.5.2  
[3bb67fe8] TranscodingStreams v0.9.6  
[5c2747f8] URIs v1.3.0  
[1cfade01] UnicodeFun v0.4.1  
[ea10d353] WeakRefStrings v1.4.1  
[efce3f68] WoodburyMatrices v0.5.5  
[fdbf4ff8] XLSX v0.7.8  
[a5390f91] ZipFile v0.9.4  
[6e34b625] Bzip2\_jll v1.0.8+0  
[83423d85] Cairo\_jll v1.16.1+0  
[5ae413db] EarCut\_jll v2.2.3+0  
[2e619515] Expat\_jll v2.2.10+0  
[b22a6f82] FFMPEG\_jll v4.4.0+0  
[f5851436] FFTW\_jll v3.3.10+0  
[a3f928ae] Fontconfig\_jll v2.13.93+0  
[d7e528f0] FreeType2\_jll v2.10.4+0  
[559328eb] FriBidi\_jll v1.0.10+0  
[0656b61e] GLFW\_jll v3.3.5+1  
[78b55507] Gettext\_jll v0.21.0+0  
[7746bdde] Glib\_jll v2.68.3+1  
[3b182d85] Graphite2\_jll v1.3.14+0  
[2e76f6c2] HarfBuzz\_jll v2.8.1+1  
[905a6f67] Imath\_jll v3.1.2+0  
[1d5cc7b8] IntelOpenMP\_jll v2018.0.3+2  
[c1c5ebd0] LAME\_jll v3.100.1+0  
[dd4b983a] LZO\_jll v2.10.1+0  
[e9f186c6] Libffi\_jll v3.2.2+1  
[d4300ac3] Libgcrypt\_jll v1.8.7+0  
[7e76a0d4] Libglvnd\_jll v1.3.0+3  
[7add5ba3] Libgpg\_error\_jll v1.42.0+0  
[94ce4f54] Libiconv\_jll v1.16.1+1  
[4b2f31a3] Libmount\_jll v2.35.0+0  
[38a345b3] Libuuid\_jll v2.36.0+0  
[856f044c] MKL\_jll v2021.1.1+2  
[e7412a2a] Ogg\_jll v1.3.5+0  
[18a262bb] OpenEXR\_jll v3.1.1+0  
[458c3c95] OpenSSL\_jll v1.1.10+0  
[efe28fd5] OpenSpecFun\_jll v0.5.5+0  
[91d4177d] Opus\_jll v1.3.2+0  
[2f80f16e] PCRE\_jll v8.44.0+0  
[30392449] Pixman\_jll v0.40.1+0  
[f50d1b31] Rmath\_jll v0.3.0+0  
[76ed43ae] SQLite\_jll v3.37.0+0  
[02c8fc9c] XML2\_jll v2.9.12+0  
[aed1982a] XSLT\_jll v1.1.34+0  
[4f6342f7] Xorg\_libX11\_jll v1.6.9+4  
[0c0b7dd1] Xorg\_libXau\_jll v1.0.9+4  
[935fb764] Xorg\_libXcursor\_jll v1.2.0+4  
[a3789734] Xorg\_libXdmcp\_jll v1.1.3+4  
[1082639a] Xorg\_libXext\_jll v1.3.4+4  
[d091e8ba] Xorg\_libXfixes\_jll v5.0.3+4  
[a51aa0fd] Xorg\_libXi\_jll v1.7.10+4  
[d1454406] Xorg\_libXinerama\_jll v1.1.4+4  
[ec84b674] Xorg\_libXrandr\_jll v1.5.2+4  
[ea2f1a96] Xorg\_libXrender\_jll v0.9.10+4  
[14d82f49] Xorg\_libpthread\_stubs\_jll v0.1.0+3  
[c7cfdc94] Xorg\_libxcb\_jll v1.13.0+3  
[c5fb5394] Xorg\_xtrans\_jll v1.4.0+3  
[9a68df92] isoband\_jll v0.2.2+0  
[0ac62f75] libass\_jll v0.15.1+0  
[f638f0a6] libfdk\_aac\_jll v2.0.2+0  
[b53b4c65] libpng\_jll v1.6.38+0  
[f27f6e37] libvorbis\_jll v1.3.7+0  
[1270edf5] x264\_jll v2021.5.5+0  
[dfaa095f] x265\_jll v3.5.0+0  
[0dad84c5] ArgTools  
[56f22d72] Artifacts  
[2a0f44e3] Base64  
[ade2ca70] Dates  
[8bb1440f] DelimitedFiles  
[8ba89e20] Distributed  
[f43a241f] Downloads  
[9fa8497b] Future  
[b77e0a4c] InteractiveUtils  
[4af54fe1] LazyArtifacts  
[b27032c2] LibCURL  
[76f85450] LibGit2  
[8f399da3] Libdl  
[37e2e46d] LinearAlgebra  
[56ddb016] Logging  
[d6f4376e] Markdown  
[a63ad114] Mmap  
[ca575930] NetworkOptions  
[44cfe95a] Pkg  
[de0858da] Printf  
[3fa0cd96] REPL  
[9a3f8284] Random  
[ea8e919c] SHA  
[9e88b42a] Serialization  
[1a1011a3] SharedArrays  
[6462fe0b] Sockets  
[2f01184e] SparseArrays  
[10745b16] Statistics  
[4607b0f0] SuiteSparse  
[fa267f1f] TOML  
[a4e569a6] Tar  
[8dfed614] Test  
[cf7118a7] UUIDs  
[4ec0a83e] Unicode  
[e66e0078] CompilerSupportLibraries\_jll  
[deac9b47] LibCURL\_jll  
[29816b5a] LibSSH2\_jll  
[c8ffd9c3] MbedTLS\_jll  
[14a3606d] MozillaCACerts\_jll  
[4536629a] OpenBLAS\_jll  
[05823500] OpenLibm\_jll  
[83775a58] Zlib\_jll  
[8e850b90] libblastrampoline\_jll  
[8e850ede] nghttp2\_jll  
[3f19e933] p7zip\_jll